BEIJING - China's environment watchdog said Tuesday that it has punished two automakers in Shandong province for producing vehicles that failed to meet emission standards.

Eight light diesel trucks produced by Shandong Kama Automobile Manufacturing Co exceeded emission standards, and 318 heavy diesel trucks had substandard pollution control devices, according to the Ministry of Environmental Protection (MEP).

The company was ordered to correct the problems and fined 31.7 million yuan ($4.9 million)

For similar offences, Shandong Tangjun Ouling Automobile Manufacture Co was fined 7 million yuan for producing 109 substandard light diesel trucks.

Emissions from vehicles are a major source of air pollution in China. A revised policy in December outlined new vehicle emission limits on carbon monoxide, hydrocarbons, nitrogen oxides and particulate matter.

A five-year national clean air action aims to improve air quality through measures such as closing factories, limiting cars and replacing coal with clean sources of energy.