Dutch police have questioned two men who arrived at Amsterdam airport from Chicago, after US authorities spotted "suspicious items" in their luggage.
One man's bags contained a mobile phone strapped to a medicine bottle, knives and watches, said US officials.
However, a spokeswoman for the US Department of Homeland Security said none of the items were dangerous "in and of themselves".
But the information was passed to the Dutch authorities, who held the men.
They were travelling on United Airlines Flight 908 from Chicago O'Hare to Amsterdam Schiphol.
Air marshals
US media reports say the men were of Yemeni origin.
One man, who started his journey in Birmingham, Alabama, was reportedly stopped there because of his "bulky clothing", ABC News reports.
Security staff found one mobile phone taped to a bottle of Pepto-Bismol, three other mobile phones taped together and several watches, also taped together. A box-cutter and three large knives were also found, ABC said.
But the man was cleared for travel, as no explosives were found, the US network said, quoting officials.
"The items were not deemed to be dangerous in and of themselves and as we share information with our international partners, Dutch authorities were notified of the suspicious items," the US Department of Homeland Security said in a statement.
Once at Chicago, one of the pair checked his luggage on a flight for Yemen but boarded the flight to Amsterdam, reports say. When officials became aware, the luggage was ordered to be removed from the Yemen-bound aircraft, media say.
US federal air marshals were travelling on the flight to the Netherlands.
NBC News reported that US concern about the incident was "low", but the authorities wanted to make sure that this was not an attempt to test airline security prior to a future attack.
A Nigerian man was detained in the US on Christmas Day 2009, after flying from Amsterdam to Detroit, and charged with trying to detonate a bomb.
