Britain's Dereck Chisora was arrested on Sunday by Munich police in the wake of his brawl with ex-champion David Haye at a post-fight press conference after Chisora lost a title fight to Vitali Klitschko.
German police detained both Chisora and his trainer Don Charles for questioning as they were preparing to board a plane back to the United Kingdom and later arrested the heavyweight boxer at Munich police headquarters.
"Given the events of Saturday evening, a criminal investigation is required," a spokesman for Munich police told SID, an AFP subsidiary.
Chisora is suspected of grievous bodily harm and threatening behaviour, the spokesman added.
Munich police also want to speak to Haye and searched his hotel room on Sunday morning, but according to sources he caught a flight back to Britain in the early hours.
The British Boxing Board of Control has already indicated they will launch an investigation into events leading up to the ugly melee in Munich when Chisora was heard to repeatedly shout that he wanted to "shoot" Haye and "burn" him.
Watch: Chisora-Haye brawl during press conference
On Saturday, Chisora lost to Klitschko in his World Boxing Council (WBC) heavyweight title bout by a unanimous points decision in Munich, but violence erupted in the post-fight press conference between Chisora and compatriot Haye.
Haye, 31, was among the reporters after working here as a pundit and branded Chisora "a loser".
The British fighter promptly left the head table at the press conference to confront Haye, who he dubbed "an embarrassment".
Haye, the former World Boxing Association (WBA) champion who was defeated on points by Vitali's brother Wladimir in July, had insisted he wants to fight Vitali on June 2 and the pair traded blows with Chisora as their respective trainers became involved.
Adam Booth, trainer of Haye and working at the fight for BBC Radio, was left with a cut head, while Haye was seen brandishing a cameraman's tripod.
Chisora was repeatedly heard shouting that he would "shoot" Haye during a barrage of expletives as the pair were separated by stunned on-lookers.
Chisora, 28, has won few friends here with his conduct after he slapped Klitschko in the face at Friday's weigh-in, then spat water in the face of his opponents brother Wladimir Klitschko, also a heavyweight champion, minutes before the title fight.
The Zimbabwe-born British fighter squared up to Vitali again after the fight verdict had been announced and received jeers and boos from the Munich crowd.
After seeing the drama unfold, Wladimir Klitschko, who holds the IBF, WBO and WBA heavyweight belts, told Sky News: "I'm totally disappointed, it went a little too far, the sport of boxing shouldn't be like that.
"Bloody faces in the news conference... fighting in the ring, not out. I'm really surprised."
Vitali, who defended his WBC title for the tenth time, despite an injured shoulder, said he did not respect Chisora as a person.
"If you are a sportsman with millions of people watching you have to set a good example, and Chisora didn't do that," Klitschko said.
"Young kids and boys were watching. I have got respect for Chisora as a fighter but no respect as a human being. He was not fair.
"I was a bit upset afterwards because I didn't knock him out.
"I really wanted to after he slapped me at the weigh-in but it didn't happen."
Chisora had earlier explained why he slapped Vitali and said: "I signed to fight Wladimir but he didn't give me a fight (Wladimir Klitschko twice pulled out injured before fighting Haye instead of Chisora).
"I was out of the ring for 18 months because of that. I told my mother that when I see one of those brothers he's going to get a slap. Vitali drew the short straw and it was him.
"But I will also give Wladimir a slap and David Haye a slap if I see him."
Moments later, Chisora and Haye were trading blows.