Investigators who will try to determine the cause of a chemical plant explosion that shook a Massachusetts neighborhood and sent four people to the hospital were waiting for clearance from structural engineers to get into the building.
The state fire marshal's office, other state agencies, local authorities and federal agencies will look into the Sunday night blast and fire at Bostik Inc., which makes adhesives and sealants, Fire Marshal Stephen Coan said Monday.
There was no word on a cause, but the explosion and four-alarm 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. 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 people were all 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.
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 house. The blast could be heard and felt for several miles around, Coan said.
Bostik, which has corporate offices in Wauwatosa, Wis., didn't immediately respond to telephone messages seeking comment on Sunday and Monday.
Beverly Peterson lives about a quarter of a 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.