MAIDUGURI, Nigeria (AP) — Assailants shot and stabbed to death 27 students in the second attack near colleges in Nigeria's troubled northeast in the last few days, school authorities said Tuesday, but police say the attacks killed 19 students and six others.

Danjuma Aiso, a student at Federal Polytechnic Mubi, a college in the town of Mubi in Adamawa State, said attackers invaded the student accommodation outside the campus between 10 p.m. Monday and 3 a.m. Tuesday.

Twenty-seven students were killed forcing the school to close Tuesday, according to Students Affairs officer Mohammed Baba Karewa who spoke to Aiso and other students.

However, Adamawa state police spokesman Ibrahim Muhammad said 25 people had been killed and that they were all men. They included 19 students of Federal Polytechnic Mubi, three students of another college, an ex-soldier, a security guard and an elderly man, Muhammad said.

Authorities believe students may have been behind the attacks, but Mubi and the surrounding region have also suffered from a spate of killings by a radical Islamist sect known as Boko Haram.

"The crisis in Mubi is suspected to have been fueled by campus politics after an election at the (college)," said Yushau Shuaib, the spokesman for the National Emergency Management Agency in a statement. Across colleges and universities in Nigeria, some fraternities have turned to gang violence to wield power on campuses.

"Boko Haram open fire sporadically," said police spokesman Muhammad. "In this case, the attackers called their victims by name, and left other people in the room alone. This is not the modus operandi of Boko Haram."

"It is the work of insiders," Muhammad said.

Police said that student elections held last week could have been the motivation for the violence.

However, Aiso said students had recently found a written warning pasted on the gate of the female hostel inside the campus and which is widely believed to have been written by members of the Boko Haram sect. The message ordered authorities to evacuate the school, he said.

The college attack follows the killing Saturday of three students outside a university campus, about 100 miles (170 kilometers) away, in the city of Maiduguri, Boko Haram's spiritual home.

Ahmed Mohammed, a spokesman for the University of Maiduguri, said Monday the university was aware of the attack but that he could not comment as it occurred off school premises.

Boko Haram has launched frequent attacks in Maiduguri and, to a lesser degree, in Mubi.

The extremist sect claimed responsibility last month for the destruction of more than 30 phone towers across Nigeria's north, including Maiduguri and Mubi. Those attacks left at least two dead in Mubi, police said, and created communications chaos in a nation that relies on mobile phones.

Boko Haram's deadly campaign has targeted mosques, churches, schools and government, security buildings and, more recently, multi-million dollar telecommunications infrastructure, but targeting students and killing them so brutally is new.

Boko Haram's name means "Western education is sacrilege" in Hausa and the group has been blamed for killing more than 690 people this year alone, according to an Associated Press count. The group wants the federal government to release its imprisoned members and implement strict Shariah law across Nigeria, which is largely divided into a Christian south and a Muslim north.