BROOKLYN, N.Y. - A blocked boiler chimney is to blame for a carbon monoxide leak that killed two people in Brooklyn earlier this week. 

City building inspectors were called to the three-story structure located at 170 Avenue O in Bensonhurst on Monday night.

Their investigation found the boiler chimney was blocked with debris.

They also discovered the building had illegal single-room occupancy units, illegal unpermitted electrical wiring, and some tenants didn't have easy access to emergency exits. 

Officials shut down the building.

The Red Cross was working with tenants forced from their homes.