A passerby snaps a photo of a building that collapsed before dawn Sunday. The area remained cordoned off as of Sunday evening. Photo: Cai Xianmin/GT

The top two floors of an eight-floor office building near the Bund partially collapsed early Sunday, local media reported.

The seventh and eighth floors of Sichuan Mansion, an L-shaped building at the corner of Yan'an Road East and Sichuan Road Middle in Huangpu district, had been undergoing interior renovations prior to the collapse, according to a report in the Xinmin Evening News.

No one was injured in the accident as workers inside the building warned other occupants that the two floors might be unstable, the report said.

Police got word at 3:01 am that the floors on the side of the building facing Yan'an Road East had fallen, according to a post on the Huangpu district government's official microblog.

The district government reported that surrounding residents and shop keepers had been evacuated, the post said. In addition, workers shut off the water, gas and electricity to the area.

"I heard two bangs and woke up. I thought there had been car crash on the Yan'an Road Elevated Highway," a resident surnamed Zhou, who lives nearby, told the Global Times Sunday.

The renovation workers, about 40 of whom were staying on the eighth floor that night, warned other occupants to leave the building after they discovered that a 2-centimeter-wide crack on one of the walls had widened to 7 centimeters that evening, a worker told Shanghai Television Station.

The collapse delayed traffic in the area, the district government said. Authorities closed parts of Sichuan Road Middle and Yan'an Road East, including the exit to the Bund Tunnel.

The Yan'an Road Elevated Highway was in gridlock during the evening rush hour.

The municipal housing authority and other authorities have created an emergency plan to demolish the remaining load-bearing structures in the top-two floors, which were added to the building in the 1980s, according to the district government.

The local government has listed the building, which was constructed in 1943, as one of the city's superior historical buildings.

The Shanghai Administration of Work Safety and local police are investigating the cause of the accident.