The group of men appeared to have been poisoned, according to country’s chief prosecutor

A group of 44 suspected members of Boko Haram who had been arrested in Chad during a recent operation against the jihadist group have been found dead in their prison cell, apparently poisoned, Chad’s chief prosecutor has announced. Speaking on national television on Saturday, Youssouf Tom said the prisoners were found dead on Thursday.

Autopsies on four dead prisoners revealed traces of a lethal substance which had caused heart attacks in some victims and severe asphyxiation in others, he said. The dead men were among a group of 58 suspects captured during a major army operation around Lake Chad launched by the president, Idriss Déby Itno, at the end of March.

“Following the fighting around Lake Chad, 58 members of Boko Haram had been taken prisoner and sent to [the capital city] N’Djamena for the purposes of the investigation. On Thursday morning, their jailers told us that 44 prisoners had been found dead in their cell,” Tom said, adding that he had attended the scene. “We have buried 40 bodies and sent four bodies to the medical examiner for autopsy.”

An investigation was ongoing to determine exactly how the prisoners had died, he said. Earlier this week, the justice minister, Djimet Arabi, told AFP the captured men had been handed over to the court system on Wednesday, and had been due in court for trial on Thursday.

A security source, speaking on condition of anonymity told AFP that “the 58 prisoners were placed in a single cell and were given nothing to eat or drink for two days”.

Mahamat Nour Ahmed Ibedou, secretary general of the Chadian Convention for the Protection of Human Rights (CTDDH), made similar accusations.

Prison officials had “locked the prisoners in a small cell and refusing them food and water for three days because they were accused of belonging to Boko Haram,” Ibedou told AFP. “It’s horrible what has happened.”

The government denied the allegations. “There was no ill-treatment,” Chad’s justice minister, Djimet Arabi, told AFP by telephone.

“Toxic substances were found in their stomachs. Was it collective suicide or something else? We’re still looking for answers,” he said, adding that the investigation was still ongoing.

One of the prisoners was transferred to hospital on Thursday, but he was “faring much better” and had rejoined “the other 13 prisoners still alive and who are doing very well,” the minister said.

The military operation against Boko Haram killed more than a thousand of the group’s militants and cost the lives of 52 soldiers, a Chadian army spokesman said. The operation ran from 31 March to 8 April.

It was launched in response to a devastating attack on Chadian troops on 23 March on a base at Bohoma, in the Lake Chad marshlands, which killed 98 soldiers. It was the largest-ever one-day loss suffered by the army.

Idriss warned his allies in the region that Chad’s army will no longer take part in operations outside the country.