Knoxville arrested after grenade gag

'Jackass' star Johnny Knoxville has been detained at Los Angeles airport for reportedly carrying a fake grenade in his bag.

The funnyman was arrested on Thursday morning at LAX airport after security guards discovered a suspicious-looking item in his luggage.

When the object was found to be a banned replica weapon, Knoxville was detained, cited for carrying a "prohibited item" through an airport and released by police, according to TMZ.com.