At least 16 people were killed after an overloaded bus veered off an icy highway bridge in China's southwestern Guizhou province on Wednesday, state media reported.

The 50-seat tourist bus packed with 56 people fell off the bridge and plunged into a valley on Wednesday afternoon, the official Xinhua news agency said.

The injured were rushed to a local hospital and an investigation into the cause of the accident has been launched.

The accident happened while the bus was travelling on an icy patch of the Lanzhou-Haikou expressway, it said.

The fatal crash was the latest on China's notoriously dangerous roads, where drivers often flout traffic safety laws.

In December, 15 primary school children died when the bus they were travelling in rolled into a river. That incident followed the deaths of 19 children in the previous month in an overcrowded, nine-seater bus.

Almost 70,000 people died in road accidents in China in 2010 -- around 190 fatalities a day -- according to police statistics.

China overtook the United States in 2009 to become the world's largest auto market.