LANZHOU - A vehicle carrying railway construction workers overturned in northwest China's Gansu Province Saturday, killing 21 people and injuring seven others, local authorities said.

The accident happened at about 7:30 am in the Manwa Township in Lintao County, when the vehicle was travelling to a railway construction site, the Gansu Provincial Work Safety Administration announced in a statement.

It was not immediately known about how many workers were aboard the vehicle.

Local authorities are investigating the cause of the accident, the statement said.