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 Monday.Witnesses described a mass of red earth and mud racing towards the park in the city of Shenzhen in ‘huge waves’ 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 was allegedly illegally stored in piles 100 meters (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 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.Map locating Shenzhen, China where dozens are missing Sunday after a landslide buried 22 buildings. 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 case, 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.‘I saw red earth and mud running towards the company building,’ one local worker was quoted by Xinhua as saying.A destroyed building after a landslide hit an industrial park in Shenzhen, south China’s Guangdo.A woman surnamed Hu told the Shenzhen Evening News Sunday that she saw her father buried by earth in his own truck. ‘It’s been hours after he was buried, and we are quite worried,’ she said. Rescue operations were slowed by numerous obstacles, including continued rain, low visibility overnight, and mud, Ao Zhuoqian, a member of the Shenzhen fire brigade involved in on-site rescue, told Xinhua. Photos showed victims wrapped in green blankets sleeping on floor pads and eating instant noodles. He Weiming, a migrant worker at a temporary shelter, said he had lost contact with 16 different friends and family members, including his parents, wife and two children, and had made dozens of phone calls to try to find them, all of which went unanswered.