BOSTON — A $56 million settlement between Massachusetts and the natural gas utility found responsible for a series of explosions and fires in the state in 2018 was approved by the state Department of Public Utilities.

The settlement with Columbia Gas of Massachusetts and its parent, NiSource, was agreed to in July and approved Wednesday, the state Executive Office of Energy and Environmental Affairs announced in a statement.

The explosions in Lawrence, Andover and North Andover in September 2018 killed one person, injured almost two dozen and damaged more than 100 buildings. Federal investigators blamed the explosions on overpressurized gas lines.

The $56 million will be used to provide debt relief to low-income natural gas customers and fund clean energy and energy efficiency measures in older homes and buildings.

The settlement also requires Columbia Gas to leave Massachusetts and transfer its assets to Eversource Energy by Nov. 1.

"Our approval of this settlement ensures that Columbia Gas is held accountable for the tragic gas incident in the Merrimack Valley, and provides needed support to the impacted communities and low-income residents," DPU Chairman Matthew Nelson said.

In separate actions, the company agreed to pay a $143 million settlement stemming from a class-action lawsuit, and a $53 million federal fine.