No-frills airline Easyjet is investigating how a passenger was able to bring ammunition on to a London-bound plane at Naples airport last night.

The alarm was raised as EasyJet flight EZY3506 was preparing to leave the Italian airport for London Stansted with 120 passengers on board.

Cabin crew saw an elderly man carrying something suspicious, searched his bag and found the rounds of ammunition, a Easyjet spokeswoman said. He was not carrying a weapon.

Italian security immediately escorted the man off the plane for questioning.

The Easyjet spokeswoman said the airline carried out a full security check and eventually took off two hours late at 10.30pm local time (8.30pm GMT).

"There was no terrorist threat here," the spokeswoman insisted. "But we will be asking why he was able to get through security with the ammunition."

The man was spotted by the cabin crew as passengers took their seats.

"The crew noticed one particular passenger who looked as though he had something suspicious in his bag," the airline's spokeswoman said.

"He was an elderly Italian gentleman. We approached him and it turned out he had some ammunition in his bag. It was a couple of rounds of ammunition.

"He didn't have any kind of weapon."

Although it is legal to travel by air with ammunition in some circumstances, it cannot be carried in hand luggage and must be checked into the hold.

"It appears that he got a little bit confused," said the Easyjet spokeswoman. "It was fairly clear from the very beginning that he was not a threat."

The plane was due to land at Stansted at 11.00pm UK time (10.00pm GMT) last night.