One of China's biggest animal-feed-producers said it had used a radio transmitter to combat crooks using drones to drop pork products contaminated with African swine-fever on its pig-farms, as part of a racket to profit from the health scare. In July, China's agriculture-ministry said criminal-gangs were faking outbreaks of swine-fever on farms and forcing farmers to sell their healthy pigs at sharply lower prices.