Three men who disappeared during a self-driving tour of Tibet have sparked searches both on land and online, as desperate family and friends use social media in an attempt to find them.

Huang Yan traveled to Tibet with two friends for a pilgrimage to pray for his mother, who is suffering from late-stage lung cancer. Huang and his friends Liu Ke and Wan Xubo set off from Zhengzhou, capital of Henan province, on July 20, but have not been in contact with anyone since July 26.

Huang's wife, Ding Jie, is three months pregnant and kept in touch with her husband through regular phone calls and his micro blog. Huang's last entry was posted at midnight on July 26, and stated he felt drowsy, was short of breath and had some chest discomfort after driving past a mountain with an altitude of 5 kilometers.