A man who was being held in a Manhattan police precinct station house on Friday was found unconscious and was rushed to Bellevue Hospital, where he was later pronounced dead, according to a city official. He is at least the fourth detainee in city custody to die in a little over a week.

The Police Department has not released the man’s name, but the official and a family friend identified him as Musa Cetin, 29. The family friend said he was a Turkish-born pedicab driver.

The deaths comes as legal and advocacy groups have been critical of what they call the city’s failure to provide adequate care for detainees with potential physical or psychological problems, particularly at Rikers Island, where two detainees died in recent days.

The city Correction Department has provided few details about those deaths, and it said it was investigating the circumstances. The two other men had been in police custody — Mr. Cetin in a holding cell at the Midtown South Precinct station house and the other man, Christopher Nieves, 46, in a holding cell at a Brooklyn courthouse. The Police Department said its force investigation division was looking into both incidents.

The police said Mr. Cetin was found unconscious and unresponsive at about 8:30 p.m. Friday inside the station house at 357 West 35th Street, and that lifesaving measures were begun immediately. He was taken by ambulance to the hospital in critical condition, the department said.

The police told family members that Mr. Cetin had hanged himself in the cell, a law enforcement official said. Some family members and friends were skeptical of that account.