A Chinese pig farm’s attempt to ward off drones – said to be spreading African swine fever – jammed the navigation systems of a number of planes flying overhead.

The farm, in northeastern China, was ordered last month to turn in an unauthorized anti-drone device installed to prevent criminal gangs dropping items infected with the disease, according to online news portal Thepaper.cn.

The device came to light after a series of flights to and from Harbin airport complained about losing GPS signals while flying over Zhaozhou county in Heilongjiang in late October. In some cases, the ADS-B tracking technology – which determines an aircraft’s position via satellite navigation – failed.

Navigation systems of planes flying over a pig farm were affected by the farmer’s efforts to prevent a drone attack by criminal gangs spreading African swine fever. (Picture: AFP)

A check on radio blockers in the area identified the farm and its owner, Heilongjiang Dabeinong Agriculture & Pastoral Foods, was ordered to turn in the equipment. No further punishment was imposed, Thepaper.cn reported. The company declined a request for comment.

Chinese state media reported last week that gangs were exploiting the African swine fever crisis by deliberately spreading the disease by using drones to drop infected items on to pig farms. The farmers are then forced to sell meat cheaply to the gangs, who then sell it on as healthy stock, according to China Comment magazine, which is affiliated to state news agency Xinhua.

In more common cases, according to the magazine, the criminals spread rumours about the presence of the virus to achieve a cheap purchase price.

Pork prices have more than doubled in China as millions of pigs have been slaughtered since the first case of African swine fever was identified in Shenyang in August last year. The disease is fatal to pigs but does not pose a threat to humans.