The FBI is probing if the men are those missing from Virginia
The FBI is investigating the arrest in Pakistan of five suspected US nationals for possible extremist links.
The men were held in a raid on a house in Sarghoda in eastern Punjab province, Pakistan's US embassy told the BBC.
The FBI said it was trying to determine whether they were the same men reported missing from their homes in the US state of Virginia late last month.
Relatives reportedly found a farewell video message, showing scenes of war and saying Muslims must be defended.
The US state department is also seeking information on the men.
Pakistani police told the BBC that the passports of the five were all American, but they are being checked to make sure they are not forged.
Three of the men are reported to be of Pakistani descent, one of Egyptian heritage and the other of Yemeni background.
The BBC's Syed Shoaib Hasan in Islamabad says that while it is not unusual for foreigners with suspected hard-line Islamic links to be arrested in Pakistan, it is unusual for Americans who may be wanted by the FBI to be detained.
"If they are American citizens, we of course are going to be very interested in the charges that they've been detained on and in what sort of circumstances they're being held," said state department spokesman Ian Kelly.
FBI spokeswoman Katherine Schweit said the agency was aware of the arrests and was in contact with the families of the missing students.
"We are working with Pakistan authorities to determine their identities and the nature of their business there, if indeed these are the students who had gone missing," she said.
The Pakistani embassy in Washington said the men were arrested in a house belonging to an uncle of one of them.
He said the house was already of interest to local police and that no charges had yet been filed against the arrested men.
US Secretary of State Hillary Clinton declined to comment on the arrests, reported the Reuters news agency, but said the US had to "work more closely with both Afghanistan and Pakistan to try to root out the infrastructure of terrorism that continues to recruit and train people".
The five students were reported missing from their homes in northern Virginia by their families in late November.
The families reportedly passed on a video to members of the US Council on American-Islamic Relations (CAIR).
Nihad Awad, the leader of CAIR, said it appeared to be "like a farewell".
"One person appeared in that video and they made references to the ongoing conflict in the world, and that young Muslims have to do something," Mr Awad told Associated Press news agency.
He said the video had made him "uncomfortable" and he had advised the men's families to contact the FBI.