Security forces are enforcing a curfew in Nigeria's north-eastern town of Mubi after at least 26 people were killed by gunmen at a student hall of residence.
Police say most victims were students called out by name by the gunmen.
A resident says the attackers went from door-to-door, shooting or stabbing.
It is unclear who is responsible.
The attack came days after dozens of people with suspected links to the Boko Haram militant group were arrested in the town.
However, officials have not ruled out a recent student union election dispute as being the trigger for the violence at Federal Polytechnic Mubi.
A BBC correspondent reports that if that proves to be the case it will shock many Nigerians, as violence amongst students has never reached this level before.
The college has been closed and some students have fled the town.