FUZHOU, July 24 (Xinhua) -- Thirteen people were killed and another seven injured after a farming vehicle plunged into a valley in southeast China's Fujian Province Tuesday morning, local authorities said.

The accident happened at about 7:50 a.m., when the farming vehicle fell off a stone bridge into the valley near Shankeng Village in Ningde City, a city government spokesman said.

It is not yet known how many passengers were aboard when the accident occurred, the spokesman said, adding that rescue efforts are under way.

The injured have been delivered to a local hospital, but the condition of their injuries is not yet known, the spokesman said.

Chinese law forbids the use of farming vehicles to carry passengers, it is not unusual, however, for farmers to travel on such vehicles in rural areas.

The cause of the accident is under investigation.