Five alleged members of the Islamist group Ansaru have gone on trial in Nigeria in connection with the kidnapping of 46 students and teachers in the state of Oyo. 

All five denied seven terrorism-related charges against them, local news agency Punch reported on Thursday, citing the country’s state security service.

Mahmud Muhammad, Abubakar Abbas, Abdulrazak Umar, Yunusa Musa, and Shamsu Sani appeared before Federal High Court Judge Salim Ibrahim in Abuja, according to Reuters. The defendants face prison terms ranging from 20 years to life if convicted, while they could face the death penalty if prosecutors prove that deaths resulted from the kidnappings under Nigeria’s 2022 anti-terrorism law.

An anonymous prosecution witness said the attack took place on May 15, when armed men targeted three schools in Oyo State’s Oriire district. The witness, identified in court only as “AAA” for security reasons, said: “School activities had just started when we heard gunshots,” according to Premium Times. She told the court that 39 pupils and seven teachers were abducted and remained in captivity for 56 days.

The witness said the captives were moved between six locations and forced to sleep on grass in rain and hot weather, Punch reported. She also said they suffered from severe shortages of food and water during their captivity. “We had to drink the dirty water just to survive,” the witness stated.

Nigerian security forces rescued 39 pupils and six teachers in July and arrested eight suspected kidnappers, the presidency said at the time. One teacher had been killed in captivity, while security personnel were wounded by explosives during an earlier rescue attempt.

Ansaru emerged as an armed splinter group of Boko Haram and publicly announced its existence in January 2012. The group maintains close ties with Al-Qaeda in the Islamic Maghreb (AQIM).

The region has been at the center of a longstanding Islamist insurgency, with mass abductions, including the 2014 kidnapping of more than 270 Chibok schoolgirls. In June, the Nigerian Army said it had rescued 360 hostages, including women and children, from a Boko Haram enclave in the state of Borno.