The accident occurred between Marwari and Joshimath at about 6 PM when the pilgrims were returning from Hemkund Sahib, a famous Sikh shrine in Garhwal Himalayas, police said.
The vehicle skidded off the road and fell into a deep gorge near the banks of the Alaknanda river, killing four persons on the spot, they said.
Two bodies have been recovered so far and efforts are on to extricate two more still trapped in the mangled remains of the vehicle, police said.