The driver of the oil tanker, bound for Upper Assam's Digboi from Guwahati, reportedly lost control of the vehicle which turned turtle near Rangaliting tea estate under Dergaon police station, a police officer said.
The tanker exploded resulting in oil leakage and a devastating fire which led to the death of three persons on the spot, while another succumbed to his injuries in the hospital today, the official said.
The dead include an elderly couple and a nine-year-old girl, the police officer said.
Meanwhile, Assam Agriculture Minister Atul Bora visited the area and announced an ex-gratia relief of Rs four lakh to the next of kin of the deceased, a government official said.