The fire, which broke out between 4 and 4.30 pm, has been brought under control, HPCL Chairman and Managing Director Subir Roy Choudhury told PTI from Mumbai.
"We don't know the cause of the fire yet," he said.
Visakhapatnam Police Commissioner B Shivadhar Reddy said 35 persons were injured in the fire that broke out at a newly built wooden cooling tower.
The tower was part of the diesel hydro desulphurisation unit (DHDS) being built at the refinery.
Choudhury said medical assistance has been rushed to the accident site and HPCL was attending to the injured, who mostly were workers.
The initial reports from the site suggested that the fire accident occurred due to blasting of cooling tower due to short circuit, sources said.
A thick layer of smoke engulfed the area causing tension and panic among nearby residents.
Fire fighting tenders from all over the city were pressed into service to control the fire, police said, adding that the injured were shifted to INS Kalyani and other nearby hospitals.
The company will take care of all medical and other expenses including compensation for the injured, a company spokesperson said.
