At least six people were injured and hundreds were ordered to evacuate their homes following a series of 70 explosions that rocked three communities near Boston on Thursday, apparently triggered by a gas pipeline rupture, local officials said.

Live TV images showed firefighters battling blazes in Lawrence, Andover and North Andover, around 25 miles (40 km)north of the U.S. city. The streets were darkened where authorities had cut off electricity and were shutting down gas service in an effort to stop further blazes.

At least three people, including one firefighter, were hurt in Andover, the town said in a statement. Six people were being treated at Lawrence General Hospital, said spokeswoman Jill McDonald Halsey. It was not immediately clear if any of those being treated at that hospital were from Andover.

Massachusetts State Police said a total of 70 fires, explosions or investigations of gas odour had been reported.

Authorities said nothing to indicate any foul play was suspected. The first explosion was triggered by an overpressurised gas line, Boston's WBZ News reported.

North Andover resident Laurie Williams, 55, said she drove home from work to find police and fire vehicles blocking streets near her home, and learned three buildings nearby were on fire.

"It was very scary," Williams said, with smoke visible on the skyline. "My first thought was this is a gas explosion."

The Columbia Gas company, a unit of NiSource Inc <NI.N>, had said earlier on Thursday that it would be upgrading gas lines in neighbourhoods across the state, including the area where the explosions occurred, but it was not immediately clear whether any work was being done in those communities."Columbia Gas is investigating what happened on its system today," said Ken Stammen, a spokesman for NiSource.

The U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) said it was dispatching a team to support the state's emergency response efforts, an agency spokesperson said on Thursday.

Local media outlets' Twitter feeds were filled with images of homes in flames or collapsed.

"We are asking everybody with gas in their homes to leave their homes until further notice," North Andover town manager Andrew Maylor told one local television station.

Lawrence Mayor Dan Rivera told WBZ: "What we know is that there are have been multiple explosions, multiple fires that are happening across the city." He said residents detecting strange odours should leave their homes.

State police urged residents served by Columbia Gas to evacuate their homes, saying the utility was cutting pressure to its lines and that it would take "some time" to shut off all service.

Agencies