Boko Haram militants gunned down dozens of students at an agricultural college in Gujba, northeast Nigeria, on Saturday night.
The students were shot while they slept in dormitories, before their classrooms were torched.
The Associated Press reported that at least 50 students were killed in the attack that began in the middle of the night.
The death toll has not been confirmed by authorities, who are still investigating.
Forty-two bodies have already been collected by the Nigerian military with 18 injured taken to nearby hospitals. Reuters put the number of bodies recovered at 26.
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The college had no security despite a mass shooting in early July in a nearby school that killed 29 students and a teacher. Some of the students were burned alive in their classrooms.
The northeast of Nigeria has been under a state of emergency since May due to the low-intensity insurgency being waged by the militant Boko Haram Islamists.
The violence has killed 1,700 people since 2010. Boko Haram seeks to carve out an Islamic state in the the country's north.
About 30,000 people have fled the violence to neighbouring Cameroon and Chad.
Boko Haram, whose name means "Western education forbidden" in a local language, has made schools the target of its attacks.
In June, two attacks on elementary schools in the region killed nine and 13 students and teachers respectively.