At least four workers were taken to a hospital and one was unaccounted for after a chemical explosion rocked an industrial park in Massachusetts early Thursday, officials said.
Fire crews responded to reports of an explosion at 9 Opportunity Way in Newburyport, about 45 miles north of Boston, at around 12:45 a.m., the Newbury Fire Department said in a news release early Thursday.
Firefighters saw that an industrial-size vat from inside the building appeared to have been thrown at least 30 feet onto an adjacent parking lot as a result of the explosion, the fire department said.
At least five workers were in the building at the time, it said. Four were taken to a hospital, where they were treated and released.
A fifth worker remained unaccounted for early Thursday, the fire department said.
The building suffered major structural damage, which prevented firefighters and technical rescue crews from entering it to begin a search, the fire department said.
The cause of the explosion was not immediately clear.
The fire department said there was no danger to area residents, but Newbury police asked workers in the industrial park to avoid Opportunity Way while operations continued.
A company called Seqens, which describes itself on its website as a "contract drug substance manufacturer," is listed online as being based at that address. The address is also listed on the company's website.
NBC News was not immediately able to independently confirm the company's location, and Seqens did not immediately respond to a request for comment.