A man found unconscious near a residential building in Burrabazar, off Netaji Subhas Road, in west-central Kolkata late on Saturday was declared dead at hospital.
Another man who was lying nearby is being treated at a hospital in Howrah.
Police identified the deceased person as Sachin Rai, 33, a resident of Howrah, who ran a courier service in Burrabazar.
The other person found unconscious was his friend Sonu Singh, a resident of Howrah. He has been admitted to a hospital with injuries on his elbow and forehead, the police said.
Based on the complaint of Rai’s family, officers of Burrabazar police station have started a murder case. Three persons named in the complaint have been arrested, the police said.
“A murder case has been started based on the specific complaint lodged by the deceased person’s family. The investigation has started and the next course of action would depend on the findings. No homicidal injuries found during preliminary investigations,” said joint commissioner (crime) Sankha Shubhra Chakrabarty.
Rai’s body underwent post-mortem on Sunday.
According to the preliminary report, the cause of his death was asphyxia due to choking from his own vomit, said an officer of Burrabazar police station.
Singh, who had injuries on him, is suspected to have fallen in an intoxicated state and hurt his elbow and forehead, police said.
“It is apparent that the two men were drinking on the road with some of their friends. Both of them were in a state of intoxication when they were found on the road sometime past Saturday midnight,” said one of the investigators.
Rai when taken to the Calcutta Medical College and Hospital was declared dead, while Singh was taken to Howrah for treatment by his family.
A senior officer attached to the case said they were collecting CCTV footage from the locality where the duo were found.
“The CCTV footage will help us know the exact sequence of events. Till now, we have found that the two men and their friends were frequently seen in the locality chatting and spending time together,” said the officer.