See photos of the scene after an explosion at a Newburyport chemical plant

A “violent explosion” at a factory in a Newburyport industrial park early Thursday morning sent four workers to a hospital and left another one dead, the city’s fire chief said.

Authorities said the factory was so badly damaged that firefighters could not reach safely reach the worker for several hours.

The worker was identified as Jack O’Keefe, 62, of Methuen, Essex District Attorney Paul F. Tucker’s office said late Thursday night.

His body was removed later Thursday night and turned over to the state medical examiner’s office, a fire department spokesman said.

See photos of the scene:

A firefighter on the site of an explosion in Newburyport.Josh Reynolds for The Boston Globe

A firefighter on the site of the explosion.Josh Reynolds for The Boston Globe

A firefighter on the site of the explosion.Josh Reynolds for The Boston Globe

A firefighter on the site of the explosion.Josh Reynolds for The Boston Globe

The site of the explosion at a pharmaceutical plant.Josh Reynolds for The Boston Globe

A firefighter on the site of the explosion at a pharmaceutical plant.Josh Reynolds for The Boston Globe

A firefighter on the scene of the explosion at a pharmaceutical plant in Newburyport. Josh Reynolds for The Boston Globe

Debris littered the scene of the explosion at a pharmaceutical plant.Josh Reynolds for The Boston Globe

A vat that was once inside a Newburyport chemical plant was hurled into the parking lot by the explosion. Keith Sullivan/Associated Press

A vat that was once inside a Newburyport chemical plant was hurled into the parking lot by the explosion.Keith Sullivan/Associated Press