Roop Kishore Agarwal, a deputy accounts manager at the refinery, was found dead in his cabin, they said.
Agarwal had last called up his family in the day and told them that he will be going for a marriage ceremony.
However, in the evening, when the office was being cleaned after closing, Agarwal's body was found on the chair in his cabin, police said.
On the complaint of his family members a report has been lodged and the body sent for postmortem.
Details about the death will be known after the postmortem, they said.