SAN FRANCISCO, Dec 30: American Muslim civil rights groups on Thursday accused US border agents of 'religion profiling' after dozens of American Muslims were searched, fingerprinted and photographed on return from an Islamic conference in Toronto.

A spokeswoman for Homeland Security's Customs and Border Protection confirmed that agents stopped anyone who said they attended the three-day conference, titled "Reviving the Islamic Spirit", based on information that such gatherings can be a means for terrorists to promote their cause.

"We have ongoing credible information that conferences such as the one that these individuals just left in Toronto may be used by terrorist organizations to promote terrorist activities, which includes travelling and fund raising," another US official said.

The American Muslim Voice (AMV) and Council on American-Islamic Relations (CAIR) - two leading American Muslim civil rights groups - said the incident was a disturbing example of religion profiling that would have a chilling effect on the constitutional rights of American Muslims.

They added that the incident particularly affected American Muslims' right to the free exercise of religion, freedom of speech, peaceful assembly, and the right to be "secure in their persons against unreasonable searches".

About 40 Muslims who were singled out for questioning and fingerprinting said that they were returning from a weekend Islamic conference of more than 10,000 in Toronto when they were stopped by US Customs and Border Protection (CBP) officials at the Lewiston Bridge crossing near Niagara Falls, New York.

Several of the Muslim citizens held at the border for up to six hours on Sunday night and Monday morning said they objected strenuously to being fingerprinted, but were informed by CBP representatives that "you have no rights", and that they would be held until they agreed to the fingerprinting procedure.

"The image of a room full of American Muslim citizens apparently being held solely because of their faith and the fact that they attended an Islamic conference is one that should be disturbing to all Americans who value religious freedom," said CAIR Executive Director Nihad Awad.

The AMV and CAIR called upon the administration to investigate this incident in order to determine the policy on fingerprinting American Muslim citizens on returning from abroad.