The Dutch defence ministry said the pilot decided to return to Schiphol after the crew had reported that several passengers on the flight to Mumbai were behaving suspiciously. The plane was escorted back to the airport by fighter jets.

"Police took off a number of people on board and took them for questioning," the ministry said.

A US government official, speaking to the Associated Press news agency on condition of anonymity, said that the passengers had been observed attempting to use mobile phones and passing phones among themselves while the airliner was taking off.

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

Airport officials said the Northwest pilot decided to turn back his 273-seat DC10-30 while it was in German airspace.
   
A spokeswoman for the airline said the rest of the 149 passengers were staying in local hotels and Northwest would fly to Mumbai on Thursday.

The defence ministry said it was keeping the national counter-terrorism coordinator informed, but the government has not decided to take any extra security measures.
   
The security alert level in the Netherlands has been at "substantial" since bombings on London's transport system last year, the second highest in a four-stage warning system.

Security has been increased at airports across the world since British police said they had foiled a plot to blow up aeroplanes in the mid-Atlantic using liquid explosives disguised as drinks.