At least 10 people were injured in a massive explosion that broke out in Indian Oil Corporation's refinery on the Agra-Delhi National Highway here on Tuesday, the police said.
Eyewitnesses reported hearing a loud explosion followed by flames shooting up from the refinery in Mathura.
Flames were visible from several kilometres away as the blaze engulfed the refinery, they said.
The powerful explosion took place around 8.30 pm while the main plant was being restarted after a month-and-a-half shutdown, sources said.
Initial reports suggest 10 to 12 workers were injured in the fire, with four individuals in a critical condition, the police said.
The injured were first taken to the refinery's hospital, where they received immediate treatment.
However, four individuals in critical condition were transferred to a private hospital in the city.
While there has been no official statement from the administration of the refinery administration or the district authorities yet, Refinery police station Inspector Sonu Kumar confirmed the incident. The explosion was heard between 8.30 pm and 9.00 pm, injuring several workers near the main plant, he said.