VIDEO: Four Injured at Middleton Explosion; Lynnfield Fire Dept. Responds

An explosion that could be felt across the North Shore  in Middleton on Sunday night, sending four employees to the hospital with what officials are calling non-life threatening injuries. 

State Fire Marshal Stephen Coan said the incident sparked a "level 3" hazmat situation.

Firefighters from several surrounding communities and throughout the North Shore, including North Andover, North Reading, Lynnfield, Peabody, Salem and Beverly, responded to the scene. Crews found a "heavy volume of fire" upon arrival shortly after 7:30 p.m., and it took between 40-50 minutes to put out, said Middleton Fire Chief Frank Twiss.

, Twiss said. Officials will continue to monitor the nearby Ipswich River to see if any chemicals spilled into the waterway, Twiss said.

All employees in the plant were accounted for, Twiss said. There were no evacuations to nearby homes, and there were no reports of any structural damage to residences, he said.

Middleton Police Chief James DiGianvittorio said his department was fielding phone calls from concerned residents hours after the initial explosion. Officials encouraged residents to check for more information in the morning.