Five people were seriously injured in an explosion at a Dow Chemical plant in North Andover, Massachusetts, on Thursday afternoon.

The blast involved the chemical trimethylaluminum, which is used to make LED lights and electronics. It is thought to have occurred when the chemical reacted with water or air.

Reports said that the explosion occurred in a lab at the rear of the building and was so powerful that it blew out a section of wall.

On Friday, hazardous materials experts and the state police bomb squad removed a container of trimethylaluminum that had been compromised in the blast.

“This is one of the more complex and larger hazmat incidents that we have responded to in recent times,” state Fire Marshal Stephen D. Coan told the Boston Globe.

He explained that the operation was complicated by the volatility of the chemical, its proximity to other dangerous materials in the facility, and the painstaking work necessary to recover it from the debris left behind by the explosion, the newspaper said.

North Andover Town Manager Andrew Maylor told WBZ-TV that there was no threat to surrounding residents and businesses as no chemicals were released into the air.

An employee was killed in an explosion at the same facility in 2013, in an incident involving a different chemical.