Roof of biochemical plant blown off in Leominster

LEOMINSTER -- An explosion blew off the roof of a biochemical building yesterday, injuring one employee and sending debris flying at least 100 yards from the site, officials said.

Residents in about 10 nearby houses were evacuated after the 4:15 p.m. explosion in the small industrial building at 28 Elm Hill Ave., on the PolyCarbon Industries Inc. campus, said a spokeswoman for Mayor Dean J. Mazzarella.

While most residents had returned to their homes by 10 p.m., Claire Freda, ward councilor for the area, expressed concern that the blast was the second at the plant to trigger an evacuation since 1997.

''People are displaced again," she said. ''This is a close-knit neighborhood, and this really affects them."

Neighbors said they could feel the explosion.

''All of a sudden the whole house shook," said college student Jeffrey Walsh, who was visiting a friend about a quarter-mile from the company. ''We thought someone hit his house. We looked up in the sky and there was a bunch of black smoke."

Walsh said he and his friend drove to the site and saw one side of the building and the roof exposed. There were pieces of the building in the road. ''When I was driving up the street, I had to avoid metal pieces," he said, describing it as sheet metal.

An explosion at the same building damaged the roof in 1997, Leominster Fire Chief Alfred E. LeBlanc said. He said that explosion happened under similar circumstances and injured two or three people.

The Worcester Telegram and Gazette reported then that the explosion burned the clothes off a technician's back.

Since then, LeBlanc said, the company has worked on smaller quantities of chemicals in the two-story building, which Fire Lieutenant Alfred Kirouac estimated to be about 35 feet by 70 feet.

The building, LeBlanc said, was designed so that the roof and rear wall would break off in case of an explosion.

Freda said that the earlier explosion led plant officials to design the building in such a way that ''it would explode safely -- if you could imagine that. This time, I don't think the neighborhood is going to be that tolerant."

The company told the neighbors the last incident was due to faulty equipment and assured them it would not happen again, Freda said. She said she plans to canvass the neighborhood today to see how neighbors want to handle the issue this time.

Water and air tests conducted after yesterday's blast showed no presence of contaminants, LeBlanc said.

Building inspectors on the scene said the building would probably have to be demolished, Kirouac said. A fire that followed the blast was put out within 30 minutes, he said.

A spokeswoman for the company, Barbara Morse, said officials did not yet know what caused the explosion.

''It isn't clear whether they were even in a manufacturing process at the time this occurred," she said.

LeBlanc said a male employee sustained burns to his face and head and was taken to Leominster Hospital. He told reporters at the scene that the injured employee had been operating a processor when he saw a flash. Morse said it was the only injury. ''Everybody has been accounted for," he said. Hazardous materials workers, the state fire marshal's office, State Police, and the Department of Environmental Protection were on the scene last night, Kirouac said.

Incorporated in 1996, PolyCarbon Industries Inc. manufactures chemical products for pharmaceutical companies, according to the company website.

The company has corporate offices and research and development laboratories in Devens.

Globe correspondents Emma Stickgold and Amanda Pinto contributed to this report. Material from Associated Press was also used.