Police arrested 12 people aboard a U.S. flight bound for India that was diverted to Amsterdam Wednesday after they displayed suspicous behavior relating to mobile phones, officials told FOX News.

Police spokesman Rob Staenacker said he could not disclose the nationalities of the people taken from the Northwest DC-10 after it was diverted over German airspace, or the nature of the suspicions against them.

"I can tell you 12 people have been arrested," he said.

It was not immediately clear if they had been charged. Suspects in the Netherlands can be held for three days without charges being issued, and, under special circumstances, can be held for an additional three days, according to local reporter Ana Uzelac, with Global News Radio.

An American passenger, who identified herself only as Alpa, told AP Television News that she saw about a dozen people taken off the aircraft in handcuffs who appeared to be of South Asian origin.

A U.S. government official, speaking on condition of anonymity, citing the sensitive nature of the subject, said that crew members and air marshals observed the passengers attempting to use cell phones and passing cell phones among themselves while the airliner was taking off.

"It was behavior that average passengers wouldn't do," the official said.

Katherine Terneulen, airport spokesperson, said passengers are allowed to carry their mobile phones onboard but cannot use them during the flight.

"We have the highest standards [of security]," she told FOX News.

The Defense Ministry said Northwest Airlines Flight NW0042 bound for Mumbai returned to Schiphol Airport after the crew grew suspicious of the behavior of several passengers.

"A number of them behaved, in the opinion of the crew, in a suspicious manner," said the ministry. "As a result, the captain asked to return to Schiphol."

After the captain radioed Amsterdam seeking permission to return with a military escort, routine security measures were swiftly put into place and the jet fighters scrambled from a northern military air field.

The plane was carrying 149 passengers when it turned around shortly after crossing the German border. A Northwest DC-10 has a normal seating capacity of 273.

The flight was canceled until Thursday, and the passengers were put up in hotels, Northwest spokesman Dean Breest said.

The Dutch National Terrorism Coordinator's Office was informed of the incident, but said there was no reason to raise the national threat level, spokeswoman Judith Sluiter said.

"It is the same as it was before — light threat," Sluiter said.

An amateur audio recording of communications between Schiphol air traffic controllers, the commercial plane's pilot and pilots of the F-16 escort planes was circulated widely among Dutch media.

Asked by an air traffic controller whether he wanted fire engines to be ready on the runway when the plane returned, the Northwest pilot replied, "no, sir."

The air traffic controller later told an F-16 pilot "the reason why he's returning to Amsterdam is unknown."

Like airports around the world, Schiphol raised the level of security two weeks ago when British police announced they had uncovered a plot to blow up several U.S.-bound commercial jetliners, but Schiphol spokeswoman Pamela Kuypers said threat levels had returned to normal.

Several alerts have been sounded since the terrorism plot was outlined 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.

The Associated Press contributed to this report.