URUMQI-- At least 20 were killed and 16 others injured after a coach bus fell off the road and plunged into a ravine Friday morning in northwest China's Xinjiang Uygur Autonomous Region, local rescuers said.

The accident occurred 10 am at a section of the national highway 219 from Xinjiang to Tibet, dubbed the most dangerous road to Tibet, said an official with Xinjiang's emergency rescue team.

There were about 40 passengers aboard the coach when the accident happened.

Among the injured, 11 were in critical conditions, the official said.

Rescue operation is underway.

No other details about the accident are available at the moment.