Prison conditions in Meru have been heavily criticised

Post-mortem examinations carried out on five of them showed that they died as a result of beatings and not suffocation as previously thought.

The prisoners suffered multiple injuries to heads, chests and ribs.

Human rights groups have called for the prisons commissioner to resign and the prosecution of those involved.

Silas M'tambu, the officer in charge of Meru prison in eastern Kenya, and his deputy, Benedict Mutunga, were placed on compulsory leave to allow "further and thorough investigations to be carried out".

The government had promised to reform Kenya's prisons after coming to power two years ago but critics say it has made little progress.

Last week, Kenya's human rights commissioner criticised conditions at overcrowded Meru jail, where 47 prisoners have died this year.

Violence

Kenya's Daily Nation newspaper has reported that the prisoners were first beaten up by warders when they refused to enter the already overcrowded cell.

The general condition of prisoners is poor

They were then attacked by other inmates when they entered the tiny 1m by 2m cell.

The prisoners suffered "blunt trauma from all directions and multiple superficial injuries", the results revealed.

The newspaper also accuses prison warders of trying to stop the chief government pathologist from conducting autopsies.

A non-governmental watchdog, the Independent Medico-Legal Unit, says it will sue the government on behalf of the families of the deceased.

Meru prison was designed to house 500 prisoners, but is holding more than 1,400 inmates.

"Whoever is implicated in the killings or injuries needs to be prosecuted," said Lawrence Mute, a member of Kenya's National Commission on Human Rights.

After the deaths, Kenya's Vice-President Moody Awori, who is in charge of prison reform, announced the transfer of some 150 prisoners - but reports say some 200 new prisoners have already arrived.

Most of the inmates in Meru prison were on remand for petty offences, waiting for their cases to be heard.

According to a recent report by Amnesty International, hundreds of Kenyans die in prison every year, some as a result of torture and some from infectious diseases caused by overcrowding.