Bucket excavator are employed to remove the relics after a seven-floor residential building suddenly collapsed in a community of Zhengzhou, capital of central China's Henan Province early Friday morning. [Xinhua]

A seven-floor residential building suddenly collapsed in a community of Zhengzhou, capital of central China's Henan Province early Friday morning, leaving at least three dead, three injured and an unknow number of others buried under the relics, Xinhua reported.

Rescue workers pull three alive from the debris and were searching for others, Xinhua said.

The report said the collapse happened at about 1:30 a.m., when residents would have been at home and sleeping. Some of them fleed before the collapse.

Chinanews.cn reported that the owner of the building added four floors to the originally three-floor building without report to relevant authorities.  

The owner could not be reached comment, and the cause was under investigation.

The rescue work is under way.