Authorities in Rio de Janeiro say three multistory buildings, including a 20-floor structure, have collapsed in the center of the city.
The cause is being investigated, but witnesses in the area at the time of the incident said there was an explosion and a strong smell of gas.
The Brazilian city's mayor, Eduardo Paes, said "a 20-story building, a 10-story building, and a smaller building of three or four floors" had been leveled.
Earlier reports mentioned an 18-story building but added that there was debris and dust all over the surrounding area, where scores of firefighters and rescue workers were working.
Paes said it was still too early to provide any casualty figures, but Brazilian television network Globo News reported at least 11 casualties and other Brazilian media claimed at least two people were dead.
Rescue workers said there were still people trapped in and under the buildings.
compiled from agency reports