But girlfriend of four months, Ashley Greene, said it was simply a cheese knife that the keen cook had packed in the wrong bag.
Appearing on Lopez Tonight, Greene, 23, explained: 'We were going from the Middle East to New York, so [there was] tons of security, tons of screenings,' 'We got through one, surprisingly enough.'
But at the second security check the security workers, 'looked at us with these stern faces like, 'What's in your bag?'' she said.
While the Twilight actress feared they were going to be arrested, Jonas simply replied: 'Whoopsies!'
'Whoopsies doesn't cut it,' she added. 'We were going to get arrested! It was embarrassing.'
Fortunately for the Camp Rock star, they let him send the offending knife to be stowed with the hold luggage.