Four months later, the death toll remains unknown. But most accounts place it between 12 and 19, with up to 40 wounded. The local morgue attendant, Georges Raymond, said that he initially registered 11 dead detainees, with several more arriving later after they died of bullet wounds at the adjacent hospital.

Prison officials would not allow The Times to enter the walled prison compound, which sits directly behind the police station in the heart of town. But reporters interviewed six witnesses to the disturbance as well as five others who visited the prison either immediately after the shootings or the next day. None saw inmates firing weapons or any evidence that inmates killed inmates. Instead, witnesses said the police shot unarmed prisoners, some in the prison yard, others in their cells. Afterward, the authorities failed to notify inmates’ relatives of the deaths, buried bodies without conducting autopsies and burned the surviving prisoners’ bloodstained clothing and shoes.

Myrtil Yonel, a human rights leader here, said, “For us, we consider this to be a massacre.”

Under a bare bulb in his office beside the prison, Olritch Beaubrun, the superintendent of the antiriot police unit, scoffed at this accusation. He said that a detainee nicknamed Ti Mousson had slaughtered inmates who resisted his escape plan.

“Ti Mousson put down the 12 detainees,” Superintendent Beaubrun said. “We did not. We never fired our guns.”

This assertion is at odds with what The Times found after reviewing confidential Haitian and United Nations reports and conducting interviews with former detainees, guards, prison cooks, wardens, police officials, judicial officials and relatives of dead prisoners.

Among other things, United Nations police officers noted that day in an internal incident report that the Haitian police had used firearms. The cooks, three women trapped inside during the riot, said that the detainees did no shooting. No weapons were recovered. Ti Mousson — whose real name is Luguens Cazeau — escaped. And the authorities did not treat the prison as the crime scene of what they portrayed as a mass murder by Mr. Cazeau, who was awaiting trial on charges of stealing a satellite dish.

The Haitian government said that it was conducting three separate investigations into the episode. But witnesses and others interviewed by The Times during two visits here last month said that they had never spoken to investigators. The inmates’ bodies had not been exhumed, and there was no indication that basic forensic evidence had ever been collected.