Fourteen people were killed and 37 others injured after a bus crashed inside an expressway tunnel in northern China, state media reported Wednesday.

The accident occurred shortly after 2:30 pm local time (0630 GMT) Tuesday, state broadcaster CCTV reported, citing local authorities in Shanxi province.

The bus, which was carrying 51 people, rammed into the tunnel's interior wall, the report said.

State news agency Xinhua confirmed the toll of those killed and injured in a separate report, without providing details on the severity of the survivors' conditions.

The cause of the incident is now under investigation, Xinhua added.

Road accidents are common in China due to a lack of strict safety controls.

In February of last year, 16 people were killed and dozens more injured in a pile-up in central Hunan province.

The month before that, 19 people died and 20 were injured in a road accident in eastern Jiangxi province.