At least 11 people were killed or injured Wednesday when an 18-story building in the center of Rio de Janeiro partially collapsed after an explosion, television reports said.

Brazilian network Globo News, citing civil defense officials, said there were "11 casualties -- dead and injured."

The building, which is located near the municipal theater on the city's Cinelandia square, collapsed after an explosion that sparked panic in the area.

Earlier, a rescue worker told AFP that construction workers who had been inside the building at the time of the incident were trapped.

Dozens of firefighters and emergency personnel were at the scene.

Thirty people who had been in an adjacent building were evacuated safely, firefighters said.