KUNMING, April 6 -- A coach bus overturned on an expressway in southwest China's Yunnan Province at around 6:00 p.m. on Monday, leaving seven people dead and 29 injured, local authority said.

The coach was heading to the provincial capital Kunming when it hit the guardrail and overturned at a segment of an expressway in Nanhua County.

Three passengers died at the scene and another four died on the way to hospital. All the 29 injured were treated in a local hospital.

Authorities are looking into the cause of the accident.