The case has bolstered fears that Americans and other Westerners are heading to Pakistan to link up with Al Qaeda and other militant groups, and it could test a U.S.-Pakistani relationship already made brittle by demands of the war in neighboring Afghanistan.
The young Muslim men, who are from the Washington, D.C., area have not yet been formally charged with any crime.
However, police are now alleging that the men were collecting and attempting to collect material to carry out terrorist activities in the list of recommended charges to be presented to a court, police official Nazir Ahmad told The Associated Press.
Those charges fall under sections of Pakistan's anti-terrorism law, and the punishments range from seven years to life in prison, the police official said in a phone interview.
The FBI is also looking into what potential charges they could face in the U.S. Possibilities include conspiracy to provide material support to a terrorist group.
U.S. Embassy spokesman Richard Snelsire declined to comment on the potential charges and would not say what efforts Washington was making to bring the men back. Snelsire did confirm that American diplomats have paid at least two consular visits to the detainees. FBI agents have also been granted some access to the men.
The men appeared before a magistrate in the Punjab province town of Sargodha on Friday. Police were given 10 more days to hold them and further investigate, said Ansar Ahmad, another Sargodha police official.
The five were arrested in Sargodha earlier this month, but are being held in Lahore, the provincial capital.
Police earlier accused them of trying to link up with militant groups and intending to go fight in Afghanistan. The detainees are accused of using the Facebook and YouTube Web sites to try to connect with extremist groups in Pakistan.
He said the police had tracked down e-mails containing clues about the men's contacts with militants, but he said police are still trying to track down a Taliban recruiter called Saifullah whom they allege was in touch with the five suspects.
Officials in both countries have said they expected the men would eventually be deported back to the United States, but the latest development muddies the picture on when that would happen. Pakistan's legal system can be slow and opaque.
The men were picked up by Pakistani authorities after their worried families in the U.S. turned to the FBI to track them down.
Pakistan officials have said those detained included two Pakistani Americans, two Ethiopian Americans and an Egyptian American named Ramy Zamzam who is a dental student at Howard University in Washington.
The others were identified as Waqar Hussain, Aman Yamar, Ahmad Abdul Minni and Umer Farooq. Pakistani officials have given various spellings of their names.
Pakistan is under U.S. pressure to do more to root out militant groups that use its soil to plan attacks against Western troops across the border in Afghanistan.
Early Friday, the Pakistani army used helicopter gunships to kill at least nine suspected militants and destroyed their hideouts in the northwest's Orakzai tribal region near the Afghan border, government official Mohammed Yasin said.
Many Pakistani Taliban fighters are believed to have fled to Orakzai since the army launched a major offensive against them in the South Waziristan tribal region in October.
Prime Minister Yousuf Raza Gilani has also hinted the army will pursue a full-scale offensive in Orakzai. The U.N. says around 40,000 people have already fled the region.