Passengers aboard a Northwest Airlines plane bound for Mumbai and forced to turn back to Amsterdam said air marshals swooped after 12 people began fidgeting with mobile phones and plastic bags, Dutch media said on Thursday.
The 12 were arrested on Wednesday after the plane landed at Amsterdam's Schiphol Airport. Prosecution authorities said they were still holding the 12 but would not give their identities or nationalities.
"I saw the air marshals run and I knew something was amiss," a 31-year-old businessman aboard the plane told Dutch newspaper Algemeen Dagblad.
"Some had beards, others were unshaven, one was wearing a robe. Some had baseball caps," another passenger told the paper.
Other passengers commented those arrested were from Asia and aged between 25 and 35.
Two Dutch F-16 fighter jets accompanied the 273-seat Northwest DC10 plane which had reached German airspace en route to Mumbai before it was forced to turn back to Schiphol.
The same flight departed for Mumbai, India's financial hub, on Thursday morning at 0830 GMT after passengers spent the night in hotels.
Dutch police can hold suspects for three days without charge, extended by another three days in special circumstances.
"All 12 are still being held but we cannot give any information about their identity," said a spokesman for the Dutch public prosecutor's office.
Passenger Sarat Menon told Dutch daily De Telegraaf: "Shortly before the flight I spoke to them in a coffee bar. I didn't detect anything suspicious."
He added the situation later on the plane remained calm throughout.
Security has been increased at airports worldwide in the last two weeks after British police said they had foiled a plot to blow up planes in mid-Atlantic using liquid explosives disguised as drinks.
Mumbai has also been on high alert after commuter train bombings on July 11 that killed 186 people.
The return of the Northwest plane to Amsterdam did not lead to heightened security and did not affect other flights at Schiphol -- Europe's third largest cargo airport and fourth biggest passenger hub -- an airport spokeswoman said.
