Prosecutors said Thursday they found no evidence of a terrorist threat aboard a Northwest Airlines flight to India that returned to Amsterdam, and they are releasing all 12 passengers arrested after the emergency landing.

The men, all Indian nationals, had aroused suspicions on Flight NW0042 to Mumbai because they had a large number of cell phones, lap tops and hard drives, and refused to follow the crew's instructions, prosecutors said.

Because of those actions by the passengers, the pilot of the DC-10 radioed for help shortly after takeoff Wednesday and the plane was escorted back to Amsterdam's Schiphol Airport by two Dutch fighter jets. The 12 were arrested after the plane landed.

U.S. air marshals on the flight also were suspicious of the men, U.S. officials and passengers said.

"A thorough investigation of the cell phones in the plane found that the phones were not manipulated and no explosives were found on board the plane," said a statement from the prosecutor's office in Haarlem, which has jurisdiction over the airport.

"From the statements of the suspects and the witnesses, no evidence could be brought forward that these men were about to commit an act of violence," the statement said.

The men were to be released later Thursday from a dention center at the airport and free to leave the Netherlands, prosecution spokesman Ed Hartjes said.

The incident reflected the jitters that persist in the airline industry in the two weeks since British police revealed an alleged plot to blow up several U.S.-bound airliners simultaneously using bombs crafted from ordinary consumer goods.

Hartjes said the electronic equipment the suspects possessed could have been enough to trigger an explosion, and he defended the flight crew's response. "This was a correct reaction under the circumstances," he said.

In New Delhi, Indian External Affairs Ministry spokesman Navtej Sarna said he had no comment.

Hartjes said 11 of the men had been traveling together, catching a connecting flight in Amsterdam from a South American country that he refused to identify. The 12th aroused suspicion for other unspecified reasons, he said. He refused to give personal details about any of them.

Passengers described the men as between 25 and 35 years old and speaking Urdu, the language commonly spoken in Pakistan and by many of India's Muslims. Some had beards, and some wore a shalwar kameez, a long shirt and baggy pants commonly worn by South Asian Muslims.

The Algemeen Dagblad newspaper quoted an unidentified 31-year-old Dutch businessman as saying the suspects were walking up and down the isle after takeoff.

"I saw the air marshals walking, and then you know something's wrong," it quoted him as saying.

Nitin Patel of Boston, who sat behind the men, told the paper: "I don't know how close we were, but my gut tells me these people wanted to hijack the airplane."

The mass-circulation De Telegraaf reported that passenger Sarat Menon quoted the men as saying they were returning from a vacation in Tobago.

"It wasn't immediately clear what was going on. There was no panic. A flight attendant told us to remain seated and to follow the air marshals' orders," Menon said.

The Northwest captain radioed Amsterdam seeking permission to return with a military escort, and jet fighters were scrambled from a northern military air field.

The national anti-terrorism office said it saw no reason to raise the country's threat level.

In a recording of air control communications, the pilot declined an offer to put fire engines on standby for the unscheduled landing at Schiphol.

The security alert was the latest of several incidents reported since the alleged terrorism plot was revealed in London. On Friday, a British plane made an emergency landing in southern Italy after a bomb scare, and the U.S. Air Force scrambled jets to escort a United Airlines flight from London to Washington as it was diverted to Boston.

On Tuesday, a flight to New York from Atlanta was diverted to Charlotte, N.C., after a flight attendant found a bottle of water and then smelled something suspicious on the plane. Officials found nothing hazardous.