The first body was pulled today from the rubbles of construction sites collapsed due to one of China's worst landslides that hit an industrial park in the country's manufacturing hub, with hundreds of rescuers mounting a massive operation to find 85 people still missing.

Citing an initial probe about the disaster which left 85 people missing, the Chinese Ministry of Land and Resources said large amount of soil and waste from the Hongao construction site was dumped there.

The body recovered this morning was the first confirmed death, with the chance of finding survivors decreasing by the hour.

Using life detectors, excavators and drones about 3,000 rescue worker carefully dug through the nearly five-storey mud pile stretching up to 10 football fields for survivors.

The rescuers were close to reaching the first floor of a buried office building last evening, the report said.

Experts flown to the area for rescue operations dug five large pits through which they tried to detect signs of life using life detectors.

"The rescue is extremely difficult with mud and silt filling up the excavation," Cui Bo, a firefighter present at the scene said.

Beneath the mud lies 33 low rise buildings, 14 factories, two offices, one canteen and three dormitories of the industrial estate of Shenzhen.

The risk of landslides has existed since the opening of the dump, which was originally a quarry.

Plants were badly damaged in the exploitation of the land, leading to serious soil erosion, a report released in January by Shenzhen Zongxing Technology on the field's environmental effects said.

Workers at the site said the soil swept down from a height of 150 metres to the industrial parks, leaving over 100,000 square metres of debris with a depth of up to 10 metres.

"Risks of landslide are already there, and precautionary measures should be taken when soil waste on the hill reaches 50 metres high," a researcher surnamed Ma, who specialises in geological exploration at Shenzhen Investigation & Research Institute Co, said.

Shenzhen, a boomtown in southern China, has seen tremendous growth over the past three decades. Office and residential buildings are rising rapidly to meet the demand of the city's booming high-tech industries and growing population.

A number of subway lines are under construction or about to begin construction in the city, with the aim of adding 11 lines in the next 15 years.

With a huge amount of construction waste being produced and limited land resources, it has become a problem for Shenzhen to find places to dump the waste.

Roughly 30 million cubic meters of construction waste is produced in Shenzhen each year - more than three times the amount in 2007, when it was 9.5 million cubic metres, according to statistics from the city's environmental health department.