Edmond Mulet, UN chief Ban Ki-moon's representative in Haiti, told reporters that Preval has asked him to join an independent commission to investigate the suspected killings which is being set up.

The six-person panel, with three UN delegates and three Haitian government officials, will be appointed in the coming days, Mulet said.

The incident, revealed earlier this week by an investigation in The New York Times based on inmate testimony and a confidential UN report, took place in a prison in Les Cayes in the week after the Jan. 12 earthquake that devastated Port-au-Prince and its surroundings, killing as many as 300,000 people.

According to the report, prisoners who were not armed were made to lie down and were shot.

Police said they found the bodies after storming the prison to quell a riot and blamed the murders on a ringleader, identified as Ti Mousson, whom they claim shot fellow inmates who refused to join him in fleeing the compound.

Two prison cooks said however that they saw no bodies when police stormed the compound, and former inmate Kesnel Jeudi told the paper that police made inmates lie down and "while the prisoners were lying down — they began firing."

Jeudi told the daily the police shootings involved the settling of scores: "There were people they selected to kill."

Most accounts put the number of dead from 12 to 19, with up to another 40 inmates wounded. The bodies were buried in an unmarked grave, the Times said.

Meanwhile, the World Bank said on Friday it had canceled Haiti’s remaining debt to help the impoverished country recover from the devastating earthquake.

Haiti, the poorest country in the Western Hemisphere, will not have to repay 36 million dollars owed to the International Development Association (IDA), the bank’s fund for the poorest countries, the Washington-based institution said in a statement.