Beijing - The death toll rose to 151 in a mudslide which buried a market and several buildings in the northern Chinese province Shanxi, the state-run Xinhua news agency said Friday.

Four days after the event, more than 3,000 rescuers, armed with spades and aided by 160 mechanical diggers, continued to search for victims buried under the heaps of dirt and mud.

Heavy rain caused a dam at a waste reservoir downstream of an illegally operating iron mine to burst, officials said earlier. About 268,000 cubic metres of mud covered an area of 30.2 hectares, destroying a market, an office building and several houses.

China's government set up an accident investigation team and promised harsh punishment for those responsible for the burst dam at the Tashan mine near the town Linfen.

"It is the most grave accident that involves the largest death toll so far this year," Wan Jun, State Administration of Work Safety director and head of the investigation, was quoted as saying. "The rising accidents disclose local governments' poor supervision on work safety. Those responsible must be dealt with seriously."

The agency said police detained 13 people deemed accountable, among them the chairman of the Xinta mining company and the mine manager. Also, the Communist Party chief of Taosi township, the head of work safety and the chief engineer of Xianfen county were sacked for neglecting the duties.

Exact casualty numbers were not available on Friday. Officials rejected speculations by residents over "hundreds" of victims, but did not release estimates of their own.

The area around Tashan has several iron ore mines that employ many migrant workers from Shanxi and other provinces, making it difficult for local officials to identify the victims of the mudslide, reports said. (dpa)