His publicist has confirmed Montel inadvertently left prescription marijuana powder in his suitcase.

He was held for an hour at the airport in Frankfurt, before officials agreed to let him go after he produced a doctor's note verifying the marijuana was for medicinal purposes.

Williams, who was not arrested, suffers from multiple sclerosis and has been an outspoken advocate of medical marijuana, which he uses to manage his pain.

His spokesman Jonathan Frankel has since released a statement, which reads: "Unfortunately this is the reality faced by medical marijuana patients every day all over the world.

"Today, Montel reaffirms his commitment to fighting for sensible medical marijuana policies across the world and to fighting the stigma he and so many other seriously ill Americans face every day for simply following the advice of their doctor. Montel’s commitment to the fight for common sense marijuana reform has never been stronger."