"We're very happy people can return to their homes", Baker said. Gas service will remain shut off while officials continue investigating what caused Thursday's explosions and fires, and crews inspect the gas lines and connections to homes.
Eversource tweeted Saturday that it was working to shut off more than 8,000 gas meters, and the company said it anticipated "this critical first phase will be substantially complete" Saturday night.
He said investigators will be looking at how local Columbia Gas officials responded to a "pressure increase" in the Lawrence area that was detected at the company's pipeline control center in Columbus, Ohio, prior to the explosions and fires.
Almost all residents in the area have had power restored, he said.
The gas lines of Columbia Gas of MA, which is part of the utility company NiSource, have been the focus of investigators.
The governor said he chose to declare a state of emergency after he spoke with state and local officials, including Lawrence Mayor Dan Rivera.
Joe Hamrock, the CEO of NiSource, said "it's heartbreaking to see this devastation and this tragedy".
NiSource was working with investigators and taking "full responsibility" for the findings of the safety board's investigation, the company's chief executive, Joe Hamrock, said at a news conference Sunday. Leonel Rondon, 18, and two of his friends were in the auto when the debris struck, his family told CNN affiliate WHDH. They warned residents not to turn the meters back on themselves, not to turn on gas appliances until service is restored and to call 911 and leave their homes if they smell gas.
Columbia Gas of MA, which provides service in the affected communities, declined to comment on Sunday on what caused the leaks, saying federal investigators would decide.
NiSource is one of the largest natural gas utilities in the United States, serving more than 3.4 million customers in seven states, according to its website.
This is not the first time that a subsidiary of NiSource, the parent company of Columbia Gas of MA, has been the subject of a federal probe stemming from a disaster.