The military offensive was launched after jihadists killed nearly 100 Chadian troops on March 23 during a seven-hour attack on an island base in Lake Chad.
At least 44 Boko Haram terrorists captured by the Chadian Military in its recent operation have died of poisoning in prison.
The men, who died of severe heart asphyxiation due to poisoning according to autopsy conducted by the office of the Chadian Prosecutor, are part of a group of 58 suspects captured in the Lake Chad operation.
Chad’s Justice Minister, Djimet Arabi, debunked allegations that the captured terrorists were placed in a single cell and given no food or water after their transfer to the capital, N'Djamena.
The military offensive was launched after jihadists killed nearly 100 Chadian troops on March 23 during a seven-hour attack on an island base in Lake Chad.
It was the deadliest attack on the Chad's army by Boko Haram since their insurgency spread across the border from Nigeria several years ago.
Public prosecutor, Youssouf Tom, said the prisoners, who were being held as part of an anti-terrorism investigation, were found dead on Thursday morning.
He said, “Forty of them were buried and the other four were taken to a pathologist, whose report revealed that a lethal substance was consumed, leading to heart problems in some and severe asphyxiation amongst others.”
Arabi confirmed to AFP that investigations were ongoing.
He said, “Was it collective suicide or something else? We're still looking for answers.”
One detainee, who was taken to hospital on Thursday, had recovered and rejoined the other 13 prisoners still alive, Arabi disclosed.
The army said its eight-day operation to flush out militants from hideouts on the islands of Lake Chad was successful.