Nigerian police have denied that there have been arrests in connection with the killing of at least 26 people at a college hostel in Mubi.
But police spokesman Mohammed Ibrahim told the BBC many officers had been deployed to the north-eastern town in the search for the attackers.
Most victims were students called out by name by the gunmen who went from door-to-door, police said.
It is not clear who was behind the attack.
Some suspect the Boko Haram militant group, while police sources are linking it to a student union election, which was contested on sectarian lines.
BBC Hausa service editor Mansur Liman says the newly elected leader of the student union at the Federal Polytechnic Mubi was among those reported to have been killed.
Rivalry between different groups of students, sometimes influenced by national politics, religion and ethnicity, is not a new phenomenon in Nigeria's higher educational institutions; however, this would be the first time it has reached such a level of violence, he says.
Leadership positions on campuses can be a stepping stone for a future career in national politics, which many in Nigeria see as a licence to get rich quickly, he adds.
However, the polytechnic's deputy registrar Shuaib Aroke has denied that the killings were linked to students politics.
"It is a fallacy," he told the AFP news agency. "We are united here at polytechnic."
The town had already been under an extensive curfew, in force between 15:00 and 06:00, after a series of arrests of people with suspected links to Boko Haram last week. That curfew is continuing.
The college has been closed and some students have fled the town.
Nigeria's Senate on Wednesday condemned "in strongest terms the killing of innocent students" and urged the federal government to move quickly to apprehend the perpetrators.
An investigation is under way. Mubi is blanketed with police, who have been going house-to-house in their hunt for the attackers.
"We have many policemen and other security officials in Mubi, and since we are still investigating and searching for the suspects, by God's grace, we'll get them," Mr Ibrahim told the BBC Hausa service.
Earlier, he was reported to have said that many suspects had been detained in connection with the killings, but he denied telling journalists this.
There have also been a series of recent military sweeps across the town in the fight against Boko Haram.
The BBC's East Africa correspondent Will Ross says the operation is Mubi is being carried out by the Joint Task Force, which is supposed to be a combination of soldiers and police.
However it is clear the soldiers take the lead in these operations and the police sometimes do not have the latest information on these operations by the JTF, our correspondent says.
Reports of the Mubi attack suggest men in military uniform entered a hall of residence outside the main campus shortly before midnight on Monday and gathered the students outside their rooms. After they were killed, their bodies were left in lines outside the buildings.
Accounts of the scale of the attack vary. A local resident and a school official have been quoted as saying at least 40 people were killed - the official reportedly saying only 25 bodies were taken to the morgue because relatives took away the bodies of the other 15.
Mr Ibrahim said the police now had a figure of 26, as one person died later of their wounds.
Some of the dead in Mubi were Muslim while others were Christian. Two security guards and an elderly resident were among the victims, the police said.
A former president of the National Association of Nigerian Students, Ken Henshaw, told the BBC that the killings were "simply shocking".
But he added: "It seems to make a lot of sense that it could have been an outcome of the elections that were held the previous day.
"You may want to know that the rector of the polytechnic is from south Nigeria and he's a Christian and the fact that he is rector had caused some tensions in the institution already. And, surprisingly, the person who won the election is a Christian.
"So I think that that was a breaking-point and the whole thing just flipped over [into violence]."
Boko Haram has not yet commented on the attack. It is fighting to establish Islamic law in Nigeria and has killed more than 1,000 people in numerous attacks across northern and central areas this year.
Adamawa state has a mixed Muslim and Christian population and borders Borno state, where Boko Haram came to prominence in 2009, staging an uprising in the capital Maiduguri.
Nigeria's population is roughly evenly divided between a largely Muslim north and a mainly Christian south.