Roof of water reclamation plant collapses after explosion; 3 reportedly trapped inside

CHICAGO, Illinois -- The roof of a water reclamation district facility has collapsed after an explosion Thursday morning.

The explosion occurred at a sludge concentration building at the Calumet Water Reclamation Plant at 430 East 130th Street. Three people are reportedly trapped inside the plant. Firefighters were seen rescuing one person from the building.

WATCH: Firefighters rescue person after explosion at water plant

Firefighters rescue a person after the roof of a water reclamation plant collapsed on the Southeast Side after a reported explosion.

A spokesperson for the Metropolitan Water Reclamation District said injuries have been reported. The number and extent of the injuries is not known.

Chopper7HD flew overhead as firefighters searched the rubble as part of a search and rescue operation.

The cause of the explosion is not known.

This is a breaking news story. Please check back for updates