May 4 (UPI) -- Rescue workers are searching for a worker who has been unaccounted for since an explosion ripped through a chemical plant in Newburyport, Mass.
The explosion happened shortly before 1 a.m. Thursday at the plant, which is run by pharmaceutical ingredients manufacturer Seqens North America.
Five employees were in the building when the explosion occurred.
"Four employees were sent to the hospital for checking and were released from the hospital with no injury. One person remains unaccounted for," Seqens said in a statement.
"It's a very methodical process. We need to make sure it's safe for us to continue our search," said Newburyport Fire Chief Steve Bradbury. "Right now, we are concentrated on making a safe entry."
In 2019, the company paid the Occupational Safety and Health Administration $50,000 in fines for six safety violations.
In 2020, an explosion destroyed part of the facility's roof and the company had to pay an additional $28,000.
"I would term it as more significant than previous incidents here. There's a fairly large debris field," said Massachusetts Fire Marshall Peter Ostroskey.