Several other nearby buildings were damaged by the accident, but no casualties were reported.

The collapsed building, an audio-video wholesale market near the Bund area, began to shake in the early hours of yesterday, when work on the cross-Huangpu-River metro line M4 was going on 20 metres underground.

The rattling sound made two guards, on night duty inside the building, call the police around 6 am, according to a man surnamed Xu, who lives in the neighbourhood.

After people were evacuated, the building later began to show more signs of a collapsing, as its windows cracked and splits appeared on its walls.

Following the collapse of its interior sections, the entire building came down around 9 am, said witnesses.

Emergency rescue staff soon rushed to the site, which was immediately blocked by the police following the accident.

Power supplies were cut in the affected area where several other buildings also showed signs of collapse, and people were evacuated from them.

Mayor Han Zheng and Vice-Mayor Yang Xiong arrived later at the site to guide rescue efforts.

The cause of the accident is still under investigation, police said.

Engineering statistics at the site were collected by the metro construction staff for analysis.

According to reports from eastday.com, the accident happened because a lot of drifting sands suddenly poured into the under-construction tunnel for the metro line that night, causing the ground to subside.

(China Daily July 2, 2003)