The explosion was reported just after 6 p.m. at the Sav-More Gas Station at 220 South Main St. in Bellingham, Bellingham police said.
Firefighters and other first responders rushed to the scene to extinguish the flames and take the injured to area hospitals. Two of those harmed were taken to the burn unit at Rhode Island Hospital for more treatment, police said.
An initial investigation determined a contracting company was performing maintenance on one of the gas pumps when it exploded. All of the injured were workers for the contracting company.
Police did not release their names.
The cause of the explosion remains under investigation.
Click here to follow Daily Voice Billerica and receive free news updates.