Three unmanned aerial vehicles have been deployed by Hebei's Environment Monitoring Station to help cut down on pollution in the province.

The UAVs, two with fixed-wings and one with multi-rotors, will take aerial photographs of suspect factories and workshops to provide evidence of possible polluting activities.

Cao Yaming, an engineer at the monitoring station, said these images will then be verified and the companies concerned punished if they are found to be breaking the law.

Flying at up to 3,500 meters off the ground with a top speed of 140 kilometers per hour, the UAVs can effectively monitor mountainous areas even under poor weather conditions, according to Cao.

"They can make up for any shortfalls in human-led ground inspections and satellite remote sensing monitoring," Cao said.

"Though large in scale, satellite remote sensing is not as timely as the UAVs in obtaining information about polluters."

The use of UAVs to monitor pollution began in March last year when the Ministry of Environmental Protection carried out inspections in the city of Handan, Hebei province, and discovered that some plants' environmental protection facilities were not in operation, according to a report in Hebei Daily.

In June, the ministry's UAVs uncovered another 64 companies in various provinces that were violating environment protection law.

Other provinces that have used UAVs for environment monitoring work include Henan, Shaanxi, Shandong, and Heilongjiang.