Beijing, China: A landslide that swept through an industrial park in southern China has buried more than 30 buildings in a sea of mud, leaving 91 people missing and triggering a gas explosion, Chinese media said on Monday.

Witnesses described a mass of red earth and mud racing towards the park in the city of Shenzhen before burying or crushing homes and factories, twisting some of them into grotesque shapes, according to the official Xinhua news agency.

The landslide was caused by the improper storage of waste soil from construction sites, according to the official newspaper of the Ministry of Land and Resources.

The soil had been illegally stored in a pile 100 metres (330 feet) high at an old quarry site and turned to mud during heavy rain Sunday morning, the state-run Global Times reported.

There were 91 people missing as of 9:00 am (0100 GMT) Monday, according to officials from the city’s emergency office cited by the Shenzhen Evening News newspaper.

More than 1,500 emergency workers were involved in the rescue, and 104 fire engines were dispatched, Xinhua said.

It said debris covered more than 10 hectares (25 acres).

Industrial accidents are common in China, with safety regulations often overlooked due to corruption. An explosion in August in the port city of Tianjin that killed nearly 200 was blamed on improperly stored chemicals.

In the Shenzhen incident, about 900 people were moved out of harm’s way before the landslide struck late in the morning in the city, which borders Hong Kong. Four people have been rescued, three of whom had minor injuries.

The slide ruptured a natural gas pipeline and triggered an explosion heard about four kilometres (2.5 miles) away, Xinhua said.

Nearby gas stations have stopped supplying the pipeline and no gas leaks have been found, the Global Times cited the local fire department as saying.