The lunch crowd crammed the Hidden Kitchen for its pastrami Reuben special. Scores of deal seekers combed Zapatos's narrow aisles for such items as slippers and toothpaste. Delivery men carted boxes into the Boston Flower Exchange.

An ordinary day on Albany Street.

Yet just out of earshot from the businesses and nearby homes, earthmovers began preparing for a building that has split the neighborhood.

This month, three years after Boston University Medical Center bid on building an ultra-high-security research laboratory, the National Institutes of Health gave its final approval to a facility in which scientists will experiment with some of the planet's most lethal viruses and bacteria, including anthrax, Ebola, and plague, in hopes of finding ways to stop them.

The federal agency's decision left some neighbors worrying that their property values will plummet; others see the project as a boon for local real estate. Some say they plan to move; others welcome the new construction and hope it will help clean up some grittier parts of the neighborhood.

There are also those who have joined local groups intent on fighting the so-called ''Biosafety Level 4" lab all the way through the construction process. They've invested hopes in two legal actions, a complaint alleging environmental racism and a lawsuit contesting the state's environmental review process, and in efforts in the State House and City Hall to ban research on the virulent pathogens.

''This is not over," said Klare Allen, community organizer of Safety Net, a Roxbury-based group that has rallied neighbors against the lab. ''NIH gave approval for the construction of the facility; they have not given approval for BU to move into the facility. . . . We'll fight until the trucks come to deliver the viruses."

On the day when a front-loader began moving dirt to make space for the construction crew's trailers, Lance Hearl found himself in conflict with his landlord.

For 12 years, the owner of Back Bay Wholesale Flowers has run his business from a 7,000-square-foot office he rents at 535 Albany St., just across the street from the proposed lab. He couldn't understand why any of his neighbors would support the project.

''I can't see how this will benefit the neighborhood. Why wouldn't anyone be against this?" said Hearl, 55. ''Wouldn't this be a perfect target for a terrorist attack, lethal viruses in the middle of a city?"

University officials say the seven-story building, which they expect will win more than $1 billion in research grants over the next 20 years, will be painstakingly constructed to protect the community. They say the worst pathogens will be kept inside a self-contained unit, within the larger, 195,000-square-foot building, that will include a maze of hallways making theft difficult and an array of redundant measures to prevent accidents.

But Hearl and others worry that nothing is fully secure. As evidence, they noted the university's disclosure last year that three of its researchers in a lower-security lab were infected with the bacterium that causes tularemia.

''What if there's a fire?" Hearl said. ''What about all the new condos in the area?"

One person with arguably more to lose, Hearl's landlord, Bonnie L. Gossels, whose family has owned the five-story warehouse in the section of the South End they call New Market, contends the lab will attract jobs and help rejuvenate the area. Plus, she said, she hopes it will help stem the residential tide threatening to transform a mainly commercial neighborhood.

The new complex will create 1,300 construction jobs and 660 permanent positions, 150 of them researchers and the remainder lower-level jobs, such as lab technicians, according to Ellen Berlin, the BU Medical Center's director of corporate communications.

''We're delighted to be getting a world-class facility, one of only four of these kinds of labs in the country," said Gossels, who has attended more than a dozen community meetings about the project.

''I think it's great for Boston, and what could be a more worthy cause than developing antidotes to terrorism?"

When she was asked how she answers her tenants' concerns about such a sensitive lab being built across the street, in the middle of a city, she said: ''The lab will be like a submarine in the building. Terrorists usually look for soft targets; this will be hardened. I'm not worried."

Next door, the new owner of a large warehouse also would seem to have reason to oppose the lab. Over the next year, the Cresset Development real estate firm plans to spend $30 million converting the building into 86 condos.

Why would anyone spend as much as $599,000 for a condo that not only overlooks the Southeast Expressway and the nightly 3 a.m. parade of tractor-trailers that supply the flower market across the street, but would now be neighbor to a controversial biodefense lab?

''The young buyer likes the edginess," said William G. Curtis, a senior vice president at Cresset.

He said he supports the project and doesn't see it having any effect on sales.

''Let me tell you this: The project will be sold out in five minutes," said Curtis, adding his company already has received 1,200 inquiries about the condos, just from a sign hanging on the building. ''We think the city has taken all measures to protect public safety and, for our buyers, it's just part of the fabric of living in a city. It's what makes it an interesting place to live and work. We like to see new things built in the area."

Another prominent stakeholder in the neighborhood has a similarly rosy view.

Edward Norberg, president of the century-old Boston Flower Exchange, said he hasn't opposed the project because he sees it as a done deal, a project with too much money and federal support to stop. Also, he said, there's a potential perk to being the lab's next-door neighbor.

''Our building's not for sale, but if it was, I think this might really increase the value of our property."

Like other neighbors, Norberg has a few worries about the project, but his concern is more for his business: A terrorism alert from the Homeland Security Department, he said, could mean traffic restrictions blocking the trucks trying to supply the exchange's 17 wholesalers.

''I don't see a reason to oppose it," Norberg said. ''If there's a problem, it doesn't really matter if you're the next-door neighbor. It would wipe out everything from the exchange to the State House."

For that potentially apocalyptic reason, of course, opponents, including neighbors, community activists, public officials, environmentalists, and scientists from throughout the area, have marched, signed petitions, and appealed to the news media to spread their concerns about the project.

Between photo shoots of new coats, Mark Miller, owner of M. Miller, blamed the mayor, who has been a staunch advocate of the project. ''If the mayor thinks this is such a good idea, why doesn't he put it near his home in Hyde Park?"

Like some other neighbors on Albany Street, he has considered moving. ''When they built the Titanic, they thought it was a great boat that would never sink. It didn't take long to prove that wrong."

A block away, where once-elegant bow-front homes line Brookline Street, Brian and Susan Dunn say they're glad they're only renting their two-bedroom apartment.

''If we owned this apartment, I think the new lab would be a big cancer," said Brian Dunn, home on a recent afternoon with his two young boys. ''I don't think anyone would want to raise kids with that lab nearby. We're definitely moving."

News that construction would begin soon is just sinking in for some. Many of the people interviewed in the neighborhood say they've been too caught up in their own affairs to pay much attention to the lab.

Eric Schapero, owner of Zapatos and who has leased property on Albany Street for 23 years, said he hasn't formed any strong opinions about the lab. He said he's been too busy taking care of business to take sides.

For now, Schapero just hopes he can trust local officials, who have assured him and his neighbors they have nothing to be worried about.

''In the back of my mind, there's some fear," he said. ''But if this is part of the progress for the South End, I wouldn't want to stop it."

Three-year road to approval

Oct. 15, 2002: The National Institutes of Health invites applicants from around the country to submit proposals to build a high-level biocontainment research facility.

Feb. 10, 2003: Boston University Medical Center submits an application to NIH.

Sept. 30, 2003: The National Institute of Allergy and Infectious Diseases, a part of the NIH, announces BU Medical Center would be one of two recipients of federal money to construct Biosafety Level 4 labs. Officials say the University of Texas Medical Branch at Galveston would be the other.

Aug. 3, 2004: The BU Medical Center files plans with the Boston Redevelopment Authority and the state's Executive Office of Environmental Affairs.

Nov. 17, 2004: The state's secretary of environmental affairs approves the final environmental impact report for the biolab.

Dec. 15, 2004: The Boston Redevelopment Authority board grants final approval for the lab.

Jan. 12, 2005: Boston's Zoning Board of Appeal approves the lab.

Jan. 12, 2005: Ten residents file a lawsuit against Boston University, the Boston Redevelopment Authority, and the state Division of Capital Asset Management in Suffolk Superior Court, stating the land transfer and the lab's approval process violates state environmental rules. A hearing was held this month on the lawsuit's merits. A decision could take months.

July 11, 2005: The Lawyers' Committee for Civil Rights Under Law files a complaint with the US Department of Health and Human Services on behalf of 14 residents of Roxbury and the South End, stating the lab's location violates the federal Civil Rights Act. The advocacy group is awaiting the results of an investigation by the agency's Office for Civil Rights, a spokeswoman said.

Feb. 2, 2006: The NIH concludes its environmental review process and announces BU Medical Center can begin using the agency's $128 million grant to build the biolab.

DAVID ABEL

David Abel can be reached at dabel@globe.com.