"Zeeshan was nabbed by the police in connection with a loot case last night and he died inside the lockup under mysterious circumstances today," Additional Superintendent of Police Vipin Mishra said.
Zeeshan's kin alleged he died due to police atrocities and the matter was being probed, Mishra said.
Deceased's brother has filed a case against inspector and three other policemen, Superintendent of Police Aparna Kumar said.
"A departmental inquiry has been ordered against the four accused," the SP said.
Meanwhile, agitated kin of the deceased thrashed some policemen in a hospital where his body was brought for the post mortem examination, police said.