UFC star Israel Adesanya has been apprehended and taken into custody by the police in New York.
According to local media, he was arrested on Wednesday shortly after arriving at John F. Kennedy Airport.
He was reportedly found in possession of metal knuckle while trying to go through security.
Brass knuckles are illegal in the United States and Adesanya could face up to one year in prison if convicted, an official said.
The incident occurred at about 1:57 p.m. local time as Mr Adesanya was undergoing security check at a terminal used by American Airlines, multiple local media reports said.
It was unclear if an appearance ticket was issued or if Adesanya would be detained in custody until initial court appearance, which has not yet been scheduled.
The destination of Adesanya when the incident occurred was also unknown, although the boxing champion of Nigerian origin lives in New Zealand.