BEIJING (Reuters) - China has detained 53 people in connection with a landslide that killed 73 people last year in the southern city of Shenzhen, the official Xinhua news agency said on Friday, citing a State Council investigation.

Investigators found that the Dec. 20 disaster, which was characterized as an "extraordinarily serious" industrial accident, occurred because too much waste construction material had been dumped in a landfill.

Fifty-seven government employees, including two high-ranking Shenzhen municipal officials, were also recommended for punishment, the news agency said.

The cabinet launched its investigation immediately after the landslide, which triggered a gas line explosion, destroyed 33 buildings and caused direct economic losses of 881 million yuan, it said.

Four people are still listed as missing and 17 people were injured, it said.

The news agency said the cause of the disaster was ineffective drainage of water at the industrial estate. A development company was also found responsible for undertaking illegal operations.

Shenzhen's district Communist Party committee and the government were also found negligent in implementing party and government guidelines and safety regulations, Xinhua said.

(This story has been refiled to remove extraneous word in paragraph three)

(Reporting by Matthew Miller; Editing by Robert Birsel)