Five people have been killed in a coal mine accident in northeast China's Heilongjiang province.

The accident happened on Monday night at the Xing'an coal mine in the city of Hegang.

According to the company that operated the mine, nine people were trapped, with four of them rescued later.

A preliminary investigation showed that the accident was caused by the leakage of liquid carbon dioxide.

The mine was run by the Hegang mining company under the Heilongjiang Longmay Group. (Reporting by Xinhua)