Al-Qaeda 'rejected US Muslims because they lacked references'
Usman Anwar, the chief police officer in the eastern city of Sargodha, said the five were "directly connected" to the al-Qaeda terrorist network. "They are proudly saying they are here for jihad (holy war]," he said.
A key break in the case came not from federal agents or spies, but from parents worried their sons might have made a terrible decision. The families, from the Washington DC area, were particularly concerned after watching what was described as a disturbing farewell video, showing scenes of war and casualties, and saying Muslims must be defended.
"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," said Nihad Awad, from the Council on American- Islamic Relations (CAIR). The video has not been made public.
After the disappearance of the five men late last month, their families, members of the local Muslim community, sought help from CAIR, which put them in touch with the FBI and got them a lawyer.
One of the men, Ramy Zamzam, is a dental student at Washington's Howard University. Pakistani police officer Tahir Gujjar identified the others under arrest as Eman Yasir, Waqar Hasan, Umer Farooq and Khalid Farooq. They were arrested on Wednesday at a house in Sargodha linked to the Jaish-e-Mohammed organisation.
Investigators are sharing their findings with FBI officials now in Sargodha.
On the heels of charges against a Chicago man accused of plotting international terrorism, the case is being seen as another sign that Americans can be recruited within the United States to enlist in terrorist networks.
President Barack Obama declined to talk specifically about the case, but warned: "We have to constantly be mindful that some of these twisted ideologies are available over the internet."
Mr Obama, in Oslo to accept the Nobel peace prize, also praised "the extraordinary contributions of the Muslim-American community, and how they have been woven into the fabric of our nation in a seamless fashion".
A Muslim leader in the state of Virginia said the five men did not seem to have become militant before they left the US. "From all of our interviews, there was no sign they were outwardly radicalised," said Imam Johari Abdul-Malik.
Pakistan has many militant groups based in its territory and the US has been pressing its government to crack down on extremism. Al-Qaeda and Taleban militants are believed to be hiding in lawless tribal areas near the Afghan border.
In Washington, a spokeswoman for the FBI said agents had been trying to help find the men.
"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.
According to officials at CAIR, the five left the country at the end of last month without telling their families.