The FBI has questioned a group of young Americans arrested in Pakistan for alleged Al-Qaeda links, as US President Barack Obama vowed an investigation into the men accused of plotting terror strikes.
Pakistani officials said five men -- arrested on Wednesday in Sargodha, south of Islamabad, at the home of a known militant -- were planning to strike "sensitive installations" in Pakistan.
Sargodha district police chief Usman Anwar, who interrogated the suspects, told AFP that they were picked up on suspicion of having links to Al-Qaeda and other outlawed extremist groups in Pakistan.
In an interview with CNN broadcast on Thursday, Anwar said: "They were there for jihad.
"They could have done anything. They had US passports. They would have access to many, many places," he added.
While Obama declined to speak specifically about the arrests, he vowed a full investigation into how and why the young men left the United States for Pakistan, possibly swept up in extremist movements.
"There will undoubtedly be a series of investigations surrounding these events, so I'd prefer not to comment on them at this point," Obama told reporters in Oslo on Thursday.
He warned of the relative ease with which members of the Muslim American community can gain access to distorted and extremist teachings on the Web.
"We have to constantly be mindful that some of these twisted ideologies are available over the Internet and can affect our young people."
Meanwhile a Muslim group in the United States said relatives of the men contacted the organisation on December 1 after they went missing from their homes close to the US capital.
Council on American Islamic Relations (CAIR) executive director Nihad Awad said the families brought along a farewell video showing one of the five men delivering a "final statement" that included war images and Koranic verses.
After viewing the video, CAIR contacted the FBI and turned over the footage and information about the missing men.
US assistant secretary of state Philip Crowley said the Pakistani authorities contacted the US embassy in Islamabad when they made the arrests.
He said a two-to-three man US embassy team, including at least one agent from the Federal Bureau of Investigation and an officer from the State Department's regional security office, met the five detainees.
"All we really know is that these individuals were in the United States until recently. They made their way to Pakistan. And beyond that... we are trying to talk to them, find out... what they were up to, what the implications are," Crowley told reporters in Washington.
"And we should let the investigation go forward before we draw any conclusions."
Asked if the US government had talked to Islamabad about extraditing or bringing the five back to the United States, Crowley replied: "Not to my knowledge. Not yet."
Secretary of State Hillary Clinton earlier told reporters that US officials had "had access" to the five.
The Pakistani authorities identified the detainees as two Pakistani-Americans, one Egyptian, one Ethiopian and one Eritrean.
"We have also arrested Khalid Chaudhry, father of the two Pakistani-American brothers aged 22 and 25 years, who is also an American national and local leader of Jaish-e-Mohammad, for harboring these five people," said Anwar.
The FBI in a statement confirmed US citizenship for four of the five who disappeared from the Washington area.
It said it was working with the families and Pakistani law enforcement "to determine their identities and the nature of their business there, if indeed these are the students who had gone missing."
A senior Pakistani security official told AFP on condition of anonymity that the men had arrived in Pakistan on November 30 from England.
"They have close links with Al-Qaeda and one of its allies in Pakistan, Lashkar-e-Jhangvi.... It can be confirmed that they had plans to strike sensitive installations in the country," he said.
Pakistan is in the grip of a fierce insurgency by Islamist extremists, with more than 2,680 people killed in attacks since July 2007.