The officials and students of Jalpaiguri based Anubhav Pratibandhi Siksha Pratisthan had gone to Mangpu in Darjeeling district to visit a house where Rabindranath Tagore had stayed.
The accident occurred when they are returning.
Police said the vehicle rolled down the hill and fell into the Teesta river at around 7 PM.
While Sunanda Mukherjee (78), a guest of the institute, died on the spot, an official identified as Gauri Chaudhuri Dutta succumbed to her injuries in a hospital.
Of the injured persons, the condition of three is stated to be critical.