A Pakistani court granted police another 10 days on Tuesday to question five Americans held on suspicion of links to Islamist militants, a government official said.
Authorities also said they had released the father of one of the five men who was arrested along with the group last week.
Police could find no evidence that father Khalid Farooq, also a U.S. citizen, had committed any crime, regional law minister Rana Sanaullah Khan said.
The men, aged 19 to 25, were reported missing from the Washington, D.C., area after their families found a farewell video showing scenes of war and casualties and saying Muslims must be defended. They were arrested in the central Pakistani city of Sargodha.
Khan said a court in Sargodha had given police 10 more days to question the group.
Police have alleged the Americans intended to join militants in the northwestern tribal areas and then travel to Afghanistan to fight against U.S. and allied forces. The case has fanned fears that Americans and other Westerners are heading to Pakistan to link up with al-Qaida and other militant groups.
The five have not been charged with any crime.