Houston, TX – HOUSTON (AP) – Authorities say at least 18 people were treated after a carbon monoxide leak at a Houston area apartment complex.

KTRK-TV reports that the Champions Fire Department says the Saturday morning leak might have been caused by a vehicle left running overnight in the garage of one of the apartment units in northwest Harris County.

Authorities say seven children are among the 18 individuals who were hospitalized. One person was taken to a hospital by helicopter. All who were hospitalized are in stable condition and expected to survive.

Residents of the apartment complex were not being allowed to return to their homes until air quality readings came back as normal.