GLENDALE HEIGHTS, Ill. (AP) — Residents of a Chicago-area apartment complex were back home Tuesday after an ammonia leak forced them to evacuate, authorities said.

The 40-unit complex in Glendale Heights was evacuated for about three hours Monday night following the ammonia leak at a nearby manufacturing plant, the Arlington Heights Daily Herald reported. Authorities were notified just after 9 p.m.

Glenside Fire Protection District officials said no injuries were reported.

Firefighters traced the leak to an outdoor ammonia tank at a powdered metal manufacturing plant.

Fire officials said the apartment complex was about 250 feet (76 meters) downwind from the business.

The plant was unoccupied at the time of the leak.

Residents were displaced while crews from the fire agency ventilated the business after firefighters located a button cutting off the leak, fire officials said.

The cause of the leak remained under investigation Tuesday.