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. 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.