Yemenis on US flight held over terror alert

Two Yemenis who arrived in Amsterdam on a flight from the US are being held on suspicion of conspiracy to commit a terrorist act, Dutch prosecutors say.

The men were detained at Schiphol airport on Monday after they were found to have checked bags onto a different, internal flight in the US.

US officials had earlier found "suspicious" items in the checked luggage but had cleared it to fly.

The US has since warned against "jumping to any conclusions".

One of the checked-in bags reportedly contained a mobile phone strapped to a medicine bottle, as well as knives and watches.

There had been speculation that the two men might have been conducting a dry-run for a potential attack.

But the officials said the incident could have been a case of misunderstanding.

"This matter is under investigation but as of right now, these two passengers have not been charged with any crime in the United States and we caution you against jumping to any conclusions," the US Department of Homeland Security (DHS) said in a statement.

Under Dutch law, the men can be held without charge for up to six days.

Bags cleared

Neither of the two, reportedly US residents, was on any watch lists. They are also not believed to know each other and were not travelling together.

One of them had been questioned on Sunday as he went through security in Birmingham, Alabama, on his way to Chicago O'Hare. He was reportedly stopped because of his "bulky clothing".

He later told officials from the US Transportation Security Administration that he was carrying a lot of cash. Screeners found $7,000 on him, but he was not breaking any law by carrying that much.

When his luggage was searched, security staff found one mobile phone taped to a medicine bottle, three other mobile phones taped together and several watches, also taped together. A box-cutter and three large knives were also found, according to ABC News.

Officials said there was no indication of explosives, so he and his luggage were cleared for the flight to O'Hare.

But DHS spokeswoman Amy Kudwa said that while the items found "were not deemed to be dangerous in and of themselves" the Dutch authorities had been notified.

At O'Hare, both men reportedly checked their luggage onto a flight bound for Sanaa, which was scheduled to stop at both Washington Dulles International Airport and Dubai.

But it appears they both either missed their connecting flight or changed their travel plans and took United Airlines flight 908 from Chicago O'Hare to Amsterdam instead. Their luggage was transferred to the Washington Dulles flight.

After security staff realised that they had not boarded the flight to Dulles, they ordered the plane back to the gate and retrieved their luggage.

'Vigorous investigation'

The men were arrested by Dutch border police shortly after their flight landed at Schiphol on Monday, said Dutch Public Prosecution spokesman Theo D'Anjou at a press conference.

The luggage which the men had taken with them on the flight to Amsterdam was searched and nothing suspicious was found.

Mr D'Anjou said they were being held in custody "on suspicion of conspiracy of a terrorist criminal act" and officials would say in the next few days whether they would be charged.

The US would be kept informed about the progress of the investigation, but no further details could be made public, he added.

The BBC's Christian Fraser in Amsterdam says that whatever the investigation into the incident eventually concludes, serious questions will be asked about the airport security in the US.

White House spokesman Robert Gibbs told CNN the US would conduct "a vigorous investigation to see if we can match up any of the circumstances that were involved with any intelligence that we might have".

"The intelligence community and law enforcement are busy looking through all of these events as we speak," he added.

Dutch and US authorities have been on alert since 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.

NBC News reported that US concern about the latest incident was "low", but the authorities wanted to make sure this was not an attempt to test airline security prior to a future attack.

The New York Times quoted a man who said he was one of the passenger's cousins and that there was an innocent explanation.