One person was killed and more than 20 people were injured in the sudden string of explosions caused by gas leaks in Lawrence, Andover and North Andover as blackish-gray clouds of smoke rolled across rooftops and flames shot into the sky.

Across the region, residents returned from work to find their homes burning and neighbors standing outside with no clear sense of what to do. Firefighters and other emergency workers raced from block to block, urging residents to evacuate to shelters that were hastily being opened. Along some blocks, the smell of gas hung in the air, and cellphones buzzed with evacuation warnings.

“It looked like Armageddon, it really did,” Michael Mansfield, the fire chief of Andover, who has worked as a firefighter for almost four decades, told a CBS station in Boston. “There were billows of smoke coming from Lawrence behind me. I could see plumes of smoke in front of me from the town of Andover. It looked like an absolute war zone.”

The string of explosions, fires and reports of gas odor — at least 70 of them, although officials were still trying to account for all of the damage late Thursday — came suddenly, beginning shortly before 5 p.m., without warning and without an immediate explanation from officials. But natural gas, and the possibility that gas had become overpressurized in a main, was the focus of many local authorities.

Earlier in the day, a local gas company, Columbia Gas of Massachusetts, announced that it was “upgrading natural gas lines in neighborhoods across the state.” Late Thursday, the company issued a statement: “Columbia Gas crews are currently responding to reports of multiple fires in Lawrence. Our thoughts are with everyone affected by today’s incident.”

This article originally appeared in The New York Times.

Katharine Q. Seelye, Farah Stockman, Jacey Fortin and Monica Davey © 2018 The New York Times