LANZHOU, Dec. 20 -- Four people were killed and seven others injured in a road accident on Friday in northwest China's Gansu Province, local police said.

The accident occurred around 9:30 a.m. on a section of highway in Pingliang City. A bus with 35 people on board crashed through a barrier and overturned due to icy conditions, killing four people on the spot, sources with the provincial traffic police authorities said.

Seven were injured and all of them have been sent to local hospitals.

Further investigation is under way.