The mishap occurred at Dharali, about 2 km away from Harshil, around 2 pm when the bus with at least 13 Russians on board, was on its way from Uttarkashi to Gangotri, police said.
The accident occurred when the tempo carrying the Russian tourists on Rishikesh-Gangotri National Highway was trying to negotiate a steep slope near Harshil and rolled down about 100 metres into the river, Uttarkashi Superintendent of Police Jagat Ram Jyoti said on phone. The vehicle which met with the accident was one of the four tempo travellers carrying a group of 47 Russians from Gangotri to Uttarkashi, the SP said.
A team of State Disaster Response Force (SDRF) personnel stationed at Harshil is searching for the lone missing Russian, he said. The other Russians tourists who were travelling in the group are being brought to Uttarkashi under police escort, he said.
Senior officials have rushed to the spot.
Bhagirathi is one of the tributaries of the Ganga.