At least 91 people were missing after a huge mound of mud and construction waste collapsed at a business park in southern China and buried 33 buildings in the country's latest industrial disaster.

Premier Li Keqiang ordered an official investigation into Sunday's landslide in the southern boomtown of Shenzhen, just across the border from Hong Kong, which comes four months after huge chemical blasts at the northern port of Tianjin killed more than 160 people.

The mudslide smashed into multi-storey buildings at the Hengtaiyu industrial park in the city's northwestern Guangming New District, toppling them in collisions that sent rivers of earth skyward.

Villager Peng Jinxin said the mud came like "huge waves", as residents ran out of the way.

"At one point the running mud was only ten metres away from me," Peng told the official Xinhua news agency.

State television showed scenes of devastation, with crumpled buildings sticking up from heaps of brown mud which stretched out across the edge of the industrial park.

The mud had covered an area of more than 380,000 sq m (72,00 sq yards) and was 10 m deep in parts, Shenzhen Vice Mayor Liu Qingsheng told reporters, according to Xinhua.

Hundreds of rescuers were sifting through rubble looking for survivors after the landslide left everything covered in mud, leaving only a surface of yellow sand visible, Xinhua said.

The Ministry of Land Resources blamed the landslide on a mountain of waste construction mud in the vicinity.

Provincial authorities sent a team to investigate and said the accumulation of a large amount of waste meant that mud was stacked too steep, "causing instability and collapse, resulting in the collapse of buildings", the ministry said in a statement.

A nearby section of China's major West-East natural gas pipeline also exploded, state television added, though it was not clear if this had any impact on the landslide.

Xinhua said the pipeline was owned by PetroChina, China's top oil and gas producer, that the 400-meter-long ruptured pipe "has been emptied" and a temporary pipe will be built.

PetroChina wrote on its microblog the pipeline blast had hit at least one industrial user, a Hong Kong power plant operated by Castle Peak Power Co Ltd, a company majority owned by a subsidiary of CLP Holdings, that has now switched to coal for power generation.

Chinese President Xi Jinping ordered provincial authorities to do everything possible to minimise casualties, treat the injured and comfort family members, Xinhua said.

Premier Li ordered central government officials to help Shenzhen authorities in the rescue, Xinhua said. Almost 3,000 rescuers were at the scene, it said, with sniffer dogs and drones.

Fourteen factories, 13 low-rise buildings and three dormitories were among the buildings flattened.

Xinhua said 14 people had been rescued and more than 900 people had been evacuated from the site by Sunday evening.

State television said that of the 91 missing, 59 were men and 32 women.

The frequency of industrial accidents in China has raised questions about safety standards following three decades of breakneck economic growth.

In one of China's worst landslides in living memory, more than 1,500 people died in 2010 when a barrage of mud slid down a mountainside into a town in the northwestern province of Gansu following torrential rain.  - Reuters