AMSTERDAM - Dutch police Monday arrested two men on a US flight whose luggage reportedly contained box cutters, knives, and a cellphone taped to a Pepto-Bismol bottle.

ABC News reported that the pair were charged with "preparing a terrorist attack," but Dutch airport police would say only that the men were arrested at Schipol airport Monday morning "at the request of the judicial police."

The US Department of Homeland Security told AFP it had informed Dutch authorities that two men travelling from Chicago to Amsterdam had packed "suspicious items" in their luggage.

But the department declined to say whether it had requested the arrest of the two men, and how and why they were allowed to board the flight despite the discovery of multiple suspect objects in at least one of their bags.

A law enforcement official speaking on condition of anonymity told AFP that neither man had "prohibited items on their persons or their carry-on luggage."

The official also said there were federal air marshals on the flight the men took from Chicago to the Netherlands.

ABC News identified the men as Ahmed Mohamed Nasser al-Soofi and Hezam al-Murisi, and said Soofi was from Yemen, citing one of the man's neighbors. The men boarded United Airlines 908 flight from Chicago, Illinois to Amsterdam despite a slew of security concerns, beginning in Birmingham, Alabama, where Soofi appears to have started his journey.

Airport screeners there reportedly stopped him because of his "bulky clothing." They uncovered he was carrying US$7,000 (S$9,500) in cash, and then opened his luggage, ABC News said.

There they found a cellphone taped to a Pepto-Bismol bottle, three cellphones taped together and several watches taped together, but because no explosives were discovered, he was cleared for the flight to Chicago.

Once at Chicago's O'Hare International Airport, he appears to have checked his luggage on a flight bound for Yemen, with scheduled stops in both Washington's Dulles airport and Dubai.

But he did not board the flight.

Instead, he was joined by Murisi, ABC said, and the pair boarded a flight to Amsterdam.

The flight carrying Soofi's luggage reportedly travelled to Washington's Dulles airport, from where it was about to depart to Dubai and then on to Yemen when officials learned his bags were on board but he was not.

The plane was ordered to return to the gate, where the baggage was removed, though officials said no explosives were detected.

Soofi and Murisi were detained when their flight arrived in Amsterdam.