Lawrence, MA – A carbon monoxide leak at a Massachusetts apartment building left around a dozen people hospitalized, including two children and two first responders.

Authorities were called to the area in Lawrence for a reported gas leak on Thursday morning.

When they arrived, the CO levels were above normal.

Four people in a third-floor apartment and seven workers at the street-level restaurant had to be evaluated, investigators said.

They say carbon monoxide detectors were not found on every floor and smoke detectors had been taken down.

Some residents were allowed to return to their homes, but the restaurant remained closed.