Finding the source

But Genzyme, based in Cambridge, said it hasn’t identified which vendor might be responsible for the contaminated supplies, making it difficult to determine how many other companies could potentially be affected. It is also unclear whether the ingredient is unique to Genzyme or is a common component in mixtures sold to other biotech companies.

“It’s a risk that is fairly impossible to evaluate,’’ Mark Trusheim, president of Co-Bio Consulting LLC, a biotechnology consulting firm in Acton, said of the potential for contamination elsewhere. “You can’t tell, given the information available.’’

Meanwhile, the Food and Drug Administration, which is responsible for inspecting drug manufacturing plants, said it is still investigating the Genzyme shutdown, which is expected to last through July while the plant is decontaminated. The agency hasn’t revealed any steps to prevent the virus from spreading elsewhere.

“It’s an open investigation,’’ said FDA spokeswoman Karen Riley. “We are collecting information.’’

On Tuesday, Genzyme reported that it discovered a virus in one of six bioreactors at its Allston plant, where it makes Cerezyme and Fabrazyme. The drugs, made using genetically engineered Chinese hamster ovary cells in large vats filled with nutrients and other chemicals, are used to treat about 8,000 patients around the world with rare genetic disorders. The conditions, Gaucher disease and Fabry disease, cause waste to build up in parts of the body, swelling organs and causing a litany of problems. The treatments, which are given intravenously about every two weeks, are extremely expensive - about $200,000 a year per patient.

Although Genzyme said the virus isn’t harmful to humans, it can impede the growth of the cells used to produce the drugs, stalling the production process. The Cerezyme and Fabrazyme the company has in inventory is not affected by the contamination, and the FDA has allowed its release for use in patients.

But because of the temporary suspension of production, Genzyme said, doses of the drugs will have to be temporarily rationed. Adult patients could be asked to skip doses - probably between two and four infusions - causing some to worry how they will be affected. Genzyme doesn’t make the drugs anywhere else in the world.

And if the virus spreads to other biotech manufacturing plants, it could potentially force those companies to shut down their production lines.

“It’s a likely scenario,’’ said Carl W. Lawton, director of the Massachusetts BioManufacturing Center at the University of Massachusetts at Lowell. “If one company has a viral infection [in its supplies], it is probably going to affect several different companies.’’

But Lawton said it may be less serious for companies that have adequate stockpiles of drugs on hand.

Several biotech companies in the region said they believe they have procedures in place to detect any contamination problems before they become serious.

Amgen Inc., one of the country’s largest biotechnology companies, said it has stringent quality control procedures to “catch potential problems early’’ at its manufacturing plant in Rhode Island.

“Such quality control procedures are a vital part of our production process,’’ said Amgen spokesman Larry Bernard. “We also have stringent inventory coverage in place to ensure we are able to supply patients in the event of a potential disruption.’’

Bernard said the company needs to take precautions because “events like this can occur in the industry,’’ due to the complexities of manufacturing drugs using living cells.

Wyeth, a drug company with a major biotech manufacturing center in Andover, said it also has procedures in place to “minimize the possibility of this type of event.’’

Abbott Laboratories Inc., which makes Humira, a drug to treat rheumatoid arthritis, at its Worcester plant, said the company has measures to test or sterilize raw materials to eliminate possible contaminants. “We’ve not had issues with viruses in Humira production in the past,’’ said Abbott spokesman Scott Stoffel.

Biogen Idec Inc., which has a small production facility in Cambridge, declined to comment.

The contamination issue also raises questions about whether Genzyme is ethically obligated to do more to warn other companies about the risk. Genzyme spokesman Bo Piela said the biotech firm has no plans to disclose the names of its suppliers, even if it traces the contamination to a single company.

“It wouldn’t be appropriate,’’ Piela said, noting that other companies haven’t publicly named their suppliers after running into similar problems. “This type of thing happens commonly in the industry.’’

But Piela said the company eventually hopes to publish information about the test it developed to identify the strain that infected the one of six bioreactors at the Genzyme plant.

The Biotechnology Industry Organization, the national trade group that represents Genzyme and other biotech companies, declined to comment. But the organization’s Statement of Ethical Principles does not appear to address the situation.

Todd Wallack can be reached at twallack@globe.com.