BEIJING, June 28 -- China has mobilized drones to gather air pollution data in key northern areas to assist an inspection on how well environmental laws are enforced, according to the Ministry of Environmental Protection.

"Images sent from these drones have a 0.04-meter resolution. In other words, we can recognize a matchbox from 1,000 meters above," said a statement released late Saturday by the ministry, citing an unnamed designer of the flying machine.

A total of 11 medium- and small-sized drones were engaged in collecting air pollution data in the provinces of Hebei and Shanxi as well as the Inner Mongolia Autonomous Region between June 16 and 27, the statement said.

They flew more than 2,000 kilometers for about 20 hours and covered over 1,000 square km during the mission, it added.

The three regions suffer comparatively more severe air pollution due to industrial development, mining and sandstorm.

"Drones can take off whenever and wherever we like to directly inspect the operations of waste-processing facilities in steel, electricity and other key industries," said Chen Shanrong, a senior official with the ministry.

According to the statement, a trial use of drones in air pollution check ran from November 2013 to February this year in several cities in Hebei, and this time's inspection saw "a relatively large-scale" operation of drones for law-enforcement inspections.

The ministry said the use of drones was "approved and greatly supported" by the country's aviation departments.

"Different types of drones were used for checking various regions and enterprises, and infrared camera technology was employed to realize around-the-clock inspection," said the statement, citing experts.

According to Chen, environmental departments will double check data gathered by drones on companies' suspected violations and collect evidence before deciding to bring violators to the book.

"Conditions have been met to use drones for law-enforcement checks on a regular basis," the statement added.