Former two-time UFC champion BJ Penn was arrested for an alleged assault in Kihei Saturday night, Maui police said Monday.

The retired mixed martial arts fighter was released pending an investigation, a police spokesman added.

Mauiwatch.com first reported that Penn, 36, was arrested late Saturday following an altercation with a friend. Police said the fight occurred about 10 p.m. outside of Kauhale’s Bar in Kihei. The alleged victim, a 37-year-old man from Kahului, has not been identified.

The Kahului man was taken to Maui Memorial Medical Center where he was treated and released, according to police. The extent of his injuries was not released.

Penn was arrested just before 11 p.m., police said. Mauiwatch.com reported he was arrested at his hotel room.

Penn, who is from Hilo, made his professional debut in mixed martial arts in 2001, and is one of only two fighters to hold Ultimate Fighting Championship  world titles in multiple weight classes.

He competed in the featherweight, lightweight, welterweight, middleweight and heavyweight divisions, and is a former UFC Lightweight Champion and UFC Welterweight Champion.

Penn retired following his third loss to Frankie Edgar in July and holds a 16-10-2 professional record.

Before beginning his fight career, Penn became the first non-Brazilian to win the black-belt division at the World Jiu-Jitsu Championships in Rio de Janeiro, Brazil.