Updated

Fifteen people died and six were injured Tuesday after a bus overturned and crashed into a deep ravine in southwestern China, officials said.

The bus, carrying 21 people, was traveling between the city of Chengdu and Maerkang County, in Sichuan Province, when it plunged about 330 feet into the valley, according to the official Xinhua news agency

The accident happened at 12:30 pm local time soon after the exit of a mountain tunnel.

The injured were taken to a local hospital.

It is not yet known what caused the crash and authorities are investigating.