Union City, NJ – Twelve people evacuated from a Union City apartment building Sunday night have returned to their homes, police said.

The building, on the 700 block of 24th Street, was evacuated at 11:43 p.m. Sunday due to high levels of carbon monoxide coming from the building’s heating system, North Hudson Regional Fire and Rescue officials told police.

Carbon monoxide is a colorless, odorless and toxic gas.

Building Department officials arrived and determined that tenants could not go back into the building because the heating system needed repairs. The 12 residents who live in the three-story building were put up in a local hotel.

Repairmen fixed the heating system and residents were allowed to return to their homes last night, police said.