At least 91 people are missing after a landslide in China buried 33 buildings in an industrial park in Shenzhen City on Sunday, Chinese officials said on Monday. 

The landslide was a man-made disaster waiting to happen after waste soil from construction sites was illegally stored in piles as high as 100 metres at the site. The soil turned into mud after heavy rains on Sunday, and poured into the Hengtaiyu Industrial Park in Shenzhen, covering an area of 380,000 square meters with silt that was 10 meters deep, Xinhua reported. 

According to Chinese media, an environmental report earlier this year had warned of an impending landslide due to the illegal piling of construction soil. 

2,906 workers are now at work to dig through the rubble to try and rescue the scores of people trapped. At least 78 excavators were deployed at the site on Monday. 

The Shenzhen landslide also caused an explosion in a 400-meter-long natural gas pipeline, forcing the owner company PetroChina to stop supplying gas on the major West-to-East pipeline. No leakage was reported.

Chinese President Xi Jinping ordered immediate rescue and relief to the people affected by the landslide. 

900 residents in the area have been evacuated and are being housed at a local sports centre, Xinhua said.

Several videos showed the moments when the massive landslide crashed into buildings, with several buildings seen crumbling into dust.