Dallas, TX – Three people were taken to the hospital after an entire residential high-rise was evacuated overnight because of a carbon monoxide leak.

The leak has since been repaired and residents have been allowed to return home.

911 calls for an “unknown odor” started just after 11:30 p.m. Monday at the 15-story high-rise located at 511 North Akard Street near San Jacinto Street.

Officials say the exact location of the leak hasn’t been found, but crews believe it was related to the building’s HVAC.