Some 70 separate fires, blasts and gas odours were reported during the incident, in which 18-year-old Leonel Rondon was killed by a falling chimney.
Firefighters spoke of having to race from one blaze to another as explosions levelled buildings in the neighbourhoods of Andover, North Andover and Lawrence.
At least 13 people were treated in hospital for injuries ranging from smoke inhalation to blast trauma.
Fire chief Michael Mansfield said investigators suspected “over-pressurisation of a gas main” caused the incident on Thursday.
He earlier described the scene as “like Armageddon”.
Brigham McCown, a former government official who once headed up the US’s Pipeline and Hazardous Materials Safety Administration, called the incident “unprecedented, at least in recent memory”.
“This has been obviously an incredibly difficult day,” the governor of Massachusetts, Charlie Baker said in a news conference in the early hours of Friday.
“At this time, the focus remains on ensuring the public safety. Once that’s complete, we will work with federal government and others to investigate how this occurred and hold the appropriate parties accountable for their actions.”
The over-pressurised mains, it was later confirmed, belonged to Columbia Gas of Massachusetts, a unit of the utility NiSource Inc based in Indiana.
Ken Stammen, a spokesman with NiSource, said Columbia Gas was investigating.
The National Transportation Safety Board – which leads on issues related to pipelines – said it had a team of investigators heading to the area. The FBI was also looking at the incident, The Boston Globe reported.
The mayor of South Lawrence, Daniel Rivera, urged residents to stay away from their homes until otherwise noted.
“There could still be a gas leak in your home,” he said. “You can’t see it and in some cases you won’t be able to smell it and God forbid, you go to sleep and don’t wake up.”