It is now safe for thousands of Massachusetts residents to return to their homes, the authorities said, three days after gas leaks touched off a series of surprise explosions and fires that killed one and injured more than 20 others.
Thousands had evacuated after a series of violent explosions Thursday afternoon. Gov. Charlie Baker of Massachusetts tweeted on Sunday that the police, firefighters and utility crews had “safely cleared” of gas thousands of homes in Andover, North Andover and Lawrence.
The authorities have not, however, explained exactly what caused the explosions, and a spokesman from the Massachusetts Emergency Management Agency did not immediately answer questions on Sunday. The National Transportation Safety Board is investigating but did not immediately return requests for comment on Sunday.
The gas lines of Columbia Gas of Massachusetts have been the focus of investigators. The authorities have previously said they were looking at the possibility that gas may have been placed under a level of pressure that was too high for the pipelines it was moving through.
The announcement on Sunday follows the completion of what the authorities are calling Phase 1 of the response to the explosions — clearing the homes of any leaked gas and restoring power to those homes.
In the next phase, the authorities will examine the damage to the gas system, and after that, they will inspect “every piece of equipment from the meter, where gas enters a building, to the equipment throughout a building that distributes gas to all the appliances,” Mr. Baker said on Twitter.
The explosions killed Leonel Rondon, 18, while he sat in a car in the driveway of a home in Lawrence, the authorities said. A chimney fell onto the car, they said, when the home, on Chickering Road, exploded.