Investigators working to determine the cause of a chemical plant explosion that shook a neighborhood and sent four people to the hospital were still waiting Monday for clearance from structural engineers to get into the building.
The blast and fire happened Sunday night at Bostik Inc., which makes adhesives and sealants. The state fire marshal's office, other state agencies, local authorities and federal agencies are investigating, and officials are also talking to plant workers, Fire Marshal Stephen Coan said.
The explosion and fire in Middleton are not considered suspicious at this point, he said.
The state Department of Environmental Management said air-quality testing found low levels of the solvent toluene at the plant but not in the surrounding residential neighborhood. Toluene is a clear, colorless liquid used in making paints, paint thinners and fingernail polish.
The environmental testing of the air and nearby Ipswich River is ongoing.
Some neighbors reported a chemical odor in the air, but Coan and Fire Chief Frank Twiss said there is no chemical threat to the public.
The four injured were workers at the plant. They went through a decontamination procedure at a hospital and were released, a hospital spokeswoman said. Their names were not released.
In a statement, Bostik said company officials are on site and fully cooperating with local authorities in the investigation.
"We are grateful to the local emergency and Hazmat personnel from the surrounding communities who so quickly and effectively responded to this urgent situation," said Bill Campbell, president and CEO of Bostik. "We have activated our crisis management procedures and will continue to collaborate with all of the necessary personnel to diligently determine the cause of this incident."
Bostik Inc is headquartered in Wauwatosa, Wis., and is part of Bostik S. A. based in France.
Homeowners near the plant described the explosion at about 7:30 p.m. as feeling like an earthquake, or like a car or tree hitting their houses. The blast could be heard and felt for several miles around, Coan said.
Beverly Peterson lives about a quarter-mile from the plant and said she felt the blast.
"Oh, yeah, it shook our house something fierce," she said.
Peterson said her son-in-law and a friend's nephew work at the plant. She said her son-in-law was working when the plant exploded but wasn't injured.
Coan said he didn't know what the workers were doing at the time of the explosion or what tasks normally happen in the building where the explosion occurred.
"We're going to talk to the workers who were there and the plant manager," he said.