(CNN) Residents returned home Friday after a natural gas leak forced evacuations Friday morning in Lawrence, Massachusetts, one of the communities hit last year by a string of gas explosions that killed at least one person.

Power was cut overnight to 1,900 homes in the city, about 30 miles north of Boston, due to the gas leak, National Grid spokesman John Lamontagne told CNN. About 80,000 people live in Lawrence.

The gas leak was traced to a line that was installed last year, though the leak's cause wasn't immediately known, Columbia Gas of Massachusetts President Mark Kempic said Friday morning.

Only 27 properties remained affected on Friday afternoon, utility officials said, and service was being restored.

No injuries, fires or explosions were reported, Lawrence Fire Chief Brian Moriarty said.

About 146 meters were affected, Lawrence Mayor Dan Rivera said. About 100 people are taking shelter at a school, he said, adding that none were impacted by last year's natural gas blasts.

The Friday incident began around 3 a.m. ET, the Lawrence Police Department told CNN. National Grid got a request to cut power at 4:30 a.m. ET, Lamontagne said.

Poor oversight caused 2018 blasts, NTSB finds

At least one person was killed last September when a string of gas explosions hit Lawrence and two other towns north of Boston. Nearly 40 homes and business were affected by the explosions and fires, and at least 22 people were taken to hospitals.

The "probable cause" of those blasts was inadequate management of a construction project by Columbia Gas, the National Safety Transportation Board announced this week. Also a factor was inadequate protection of a low-pressure natural gas distribution system, the agency concluded.

"Columbia Gas of Massachusetts' weak engineering management ... did not adequately plan, review, sequence, and oversee the construction project that led to the abandonment of a cast iron main without first relocating regulator sensing lines to the new polyethylene main," NTSB's Managing Director Sharon Bryson said Tuesday.

"Contributing to the accident was a low-pressure natural gas distribution system designed and operated without adequate over-pressure protection," she said.

Columbia Gas' findings align with those of the NTSB, the utility said in a statement.

"We welcome today's action by the NTSB because it will help us, our industry partners, the public, and others learn from this tragedy. As we've said since that tragic day, we take responsibility for what happened," the statement said.