The head of an urban enforcement agency in the Chinese district where a huge landslide left scores of people missing has killed himself, authorities said Monday.

Xu Yuan'an, head of the City Urban Administrative and Law Enforcement Bureau for Shenzhen's Guangming New District, jumped to his death late Sunday, according to a post on an official police social media account.

After an investigation police determined Xu's death was a suicide, the post said.

In a separate post Shenzhen police announced they had detained 12 people, giving few details except to say some of them were from the company that owned the landfill which caused the landslide.

Xu's was the second reported suicide Sunday after state media said the owner of a gypsum mine in eastern China killed himself after a cave-in killed one person and left 17 trapped.

Only seven deaths have been confirmed from the Shenzhen landslide, which struck the southern boom town bordering Hong Kong just over a week ago. But 75 people are still unaccounted for after more than 30 buildings were buried.

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

Soil was illegally piled 100 metres (330 feet) high at an old quarry site and turned to mud during rain, according to the state-run Global Times.

It was the latest in a series of fatal man-made accidents in the world's most populous country, coming just months after giant chemical blasts in the industrial city of Tianjin killed almost 200 people.

Urban management officials, known as chengguan in Chinese, enforce civil ordinances such as rules against street vendors or some types of pets.

But in recent years they have gained particular notoriety for abusing their power while enforcing city laws, including the beating to death of a watermelon vendor in 2013.

Xu was among the officials who approved the landfill project, according to a report by the Shenzhen Special District newspaper that was later deleted.

Cynical Internet users raised the spectre of corruption having played a role.

"There goes all the evidence," one commentator wrote. "Now we'll never know what really happened."

Another sarcastically lamented a practice where graft investigations cease if the suspect commits suicide, enabling their families to retain their assets.

"Make sure not to bother his wife and child!" added a different posting.