Beijing, Sep 19 : At least nine people were killed and six others missing after a passenger boat overturned in a river in China's Guizhou province, local authorities confirmed on Sunday. The accident took place at 4.50 p.m. on Saturday in Zangke River, reports Xinhua news agency. The ship, which had a capacity of 40 people, was overloaded when the accident happened. Authorities are yet to confirm the exact number of passengers who were on board. As of Sunday, 40 people were rescued from the river, with 31 in non-life-threatening conditions, and nine died after being rescued. Most of the passengers were students, according to the authorities. A total of 17 rescue teams and 50 boats have been dispatched to join the search and rescue operation, and an investigation into the cause of the accident is underway. /IANS