LAWRENCE, Mass. (AP) — Hundreds of residents evacuated because of a natural gas leak in a Massachusetts city affected by gas explosions and fires last year will soon be able to return home.

Lawrence Mayor Daniel Rivera said Friday that electricity and gas are gradually being restored and that the majority of residents will be allowed to return by midafternoon.

The leak was discovered around 3:15 a.m. Friday. About 150 homes were evacuated as a precaution.

Gov. Charlie Baker says state officials are still investigating but are confident that the leak is isolated and that there's no immediate public safety risk.

Mark Kempic is president of Columbia Gas. He says the utility company has repaired leaks since replacing gas lines following last September's disaster but nothing to this magnitude.