Police in Liuzhen town in Beijing's Changping district have been assigned to patrol farmlands for sand thieves who have destroyed massive patches of cropland and threatened villagers' lives, the local government said.

Farmers said the thieves have been digging up their fields under the cover of darkness and selling the sand to nine mines for industrial use, the Beijing Times reported yesterday.

Dozens of acres of cornfields in Heizhai village were turned into gaping holes, the report quoted village head Huang Chenghua as saying.

"They dug up the fields without any regard for the corn that was soon to be harvested," Huang said.

"There's no way we can grow anything in these big holes. This land is now completely useless."

The proliferation of sand thefts resulted from the soaring demand from mining plants flourishing in the surrounding area, Huang said, adding that a truckload of sand sells for about 100 yuan.

The thefts began in Heizhai in 2005 and worsened in 2006. That year, just one digging team destroyed 20 hectares - and several villagers' tombs - in a single day.

Some villagers have begun sleeping in their fields at night, but their land often ends up being destroyed anyway, as the gangs just wait until the farmers leave the fields.

Huang recalled that he and a group of villagers once tried to defend their fields by running night patrols but were threatened by the gangs.

The thieves once placed funerary wreaths in front of the village committee office and Huang's house, he said.

It was only when media picked up the issue that it began getting widespread attention.

The Changping district government recently ordered police to patrol the farmlands 24 hours a day.

Local police said an investigation team will be dispatched to the area and companies found to be involved in the sand trade would have their operations suspended.