Naushad Mohammed Hussain Khan (45), a resident of suburban Kurla, who had many cases of pick-pocketing registered against him, was taken for enquiry in connection with a new case of pick-pocketing, police said.
Khan was kept in the detection room but was not arrested and there were two other accused, held in some other cases, present, they said.
According to the police, Khan banged his head against an iron window and fell unconscious after he started bleeding profusely.
The post-mortem report is awaited and for now it is difficult to say if Khan, a drug addict, was under the influence of drugs yesterday.
"The two constables who were on duty in the detention room were suspended for negligence," the official said.