
The accident occurred shortly after 2.30pm 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.
Thirteen people were found dead at the scene, and “many” others were sent to hospital for treatment, CCTV said.
The cause of the incident is now under investigation, it 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.