Two men were being questioned today over a possible attempt to test airline security after suspicious items were found in their luggage.

The pair were arrested at Amsterdam airport after a mobile phone taped to a medicine bottle and a knife and box cutter were discovered in their suitcases.

They had arrived on a United Airlines flight from Chicago, where their decision to change their flight plans raised questions, officials said.

Ahmed Mohamed Nasser al Soofi and Hezam al Murisi were being held at the airport for questioning, but neither has been charged with any offence in the Netherlands, said a spokesman for the national prosecutor's office.

Al Soofi had a Michigan address but it was not clear where the two men were from.

Al Soofi was questioned as he went through security in Alabama on his way to Chicago.

He said he was carrying a lot of cash. Screeners found 7,000 dollars on him, but he was not breaking any law by carrying that much money.

Security also found multiple mobile phones taped together and multiple watches taped together in his checked baggage.

Al Soofi was supposed to fly from Chicago to Washington Dulles International Airport in Virginia, and then on to Amsterdam. But when he got to Chicago, he changed his travel plans to take a direct flight to Amsterdam.

Al Murisi also changed his travel plans in Chicago to take a direct flight to Amsterdam, raising suspicion among US officials. Federal Air marshals were on the flight from Chicago to Amsterdam, a law enforcement official said.

A Homeland Security spokeswoman said once officials found suspicious items in luggage associated with two passengers on Sunday night's flight, they notified the Dutch authorities.

"The items were not deemed to be dangerous in and of themselves," she said. She would not identify the passengers.

It is not illegal to carry knives or taped mobile phones and watches in checked baggage.

Security at Amsterdam has been increased this year after Umar Farouk Abdulmutallab, a Nigerian student, flew from the airport to Detroit on Christmas Day with explosives in his underwear.

Abdulmutallab tried to detonate the explosives over the United States before being grabbed by passengers and crew.

After the Abdulmutallab security lapse, Schiphol ordered 60 new full body scanners to screen passengers flying to the United States. Those who do not pass through the scanners are patted down.