Dozens of people are missing after a landslide engulfed 22 buildings at an industrial park in the southern Chinese city of Shenzhen.

HONG KONG — As rescuers searched Monday for survivors of a catastrophic landslide in the southern Chinese city of Shenzhen, a series of failures and ignored warnings that contributed to the disaster began to emerge.

The Ministry of Land and Resources said the landslide that destroyed at least 33 buildings on Sunday was caused by the collapse not of a hillside but of a sodden mountain of dirt and construction debris in an industrial area. At least 91 people were missing as of early Monday, the official Xinhua News Agency reported.

The rain-soaked material had built up for nearly two years at the site of a former quarry, Xinhua said, citing residents there.

Cell phone videos captured the moment several buildings were knocked over by the slide. Local residents have raised concerns that man-made factors may have contributed to Sunday’s landslide. The Ministry of Land and Resources said a steep man-made mountain of dirt, cement chunks and other construction waste had been piled up against a 100-meter (330-foot)-high hill over the past two years.

Heavy rains in the region saturated the soil, making it heavy and unstable, and ultimately causing it to collapse with massive force.

“The pile was too big, the pile was too steep, leading to instability and collapse,” the ministry said, adding that the original, natural hill remained intact.

An area of 20,000 sq m (24,000 square yards) was covered with soil, the Public Security Bureau’s firefighting bureau said.

The state-run Xinhua news agency quoted a local worker as saying he saw “red earth and mud running towards the company building”.

Another resident living around 4km (2.5 miles) from the site described hearing a “loud explosion” at around noon as the landslide hit.

Dozens of people are missing after a landslide engulfed 22 buildings in Chinese city of Shenzhen.

Dozens of people are missing after a landslide engulfed 22 buildings in Chinese city of Shenzhen.