GUIYANG, May 20 -- A nine-story building collapsed in Guiyang, capital of southwest China's Guizhou Province, on Wednesday. Rescuers have confirmed that there are people trapped inside, but the number of casualties is not yet known.

The accident happened at 11:30 a.m., when the apartment building with more than 30 households in the Yunyan District of Guiyang fell down.

A man surnamed Zhang who lived on the ground floor was pulled out by rescuers. He told Xinhua that he was awakened by loud noises. He was about to run from the building before being buried by falling debris.

Another resident at the scene who didn't give her name was worried about her daughter-in-law. "She lived on the ninth floor," she said. "I called, but couldn't reach her."

Residents from nearby buildings were evacuated after the accident.

The cause of the accident is being investigated.