CHENGDU, July 11 (Xinhua) -- Three people died and four remained missing after a tourist bus lost control after being hit by a stone rolled off a mountain on Thursday in southwest China's Sichuan Province.

The accident happened around 2:05 p.m. on a road in the county of Songpan in Aba Tibetan and Qiang Autonomous Prefecture.

The bus, carrying 30 people, slipped to the roadside grass after being hit. So far three people have been killed, with 18 injured. Four are missing, according to the county government.

The injured have been sent to hospital and rescue is underway.