Carl Froch has apologized for threatening to "kill" Mikkel Kessler in their IBF super-middleweight title bout in London on Saturday night.
But the British Boxing Board of Control has started an investigation into the incident.
Froch launched a strongly worded attack on his Danish opponent in a pre-fight media briefing on Wednesday.
Speaking to reporters, the Briton said: "On Saturday night, if I have to, I will kill this f***. Sorry about the language, but I will kill him.
“It sounds brutal, it sounds horrible, but this is what it means to me. I'm going to leave it in the ring. And when I'm smashing his face in, I am going to go for the kill. I am going to go for the finish."
Kessler beat Froch on points three years ago. They have since become friends, and Froch took to Twitter to apologise on Thursday.
"I'm sorry if my comments yesterday offended anyone. This fight means so much to me and emotions are running high. See you at the weigh-in."
Despite the Nottingham fighter's apology, the Board of Control’s general secretary, Robert Smith, said the governing body would investigate the comments.
"Carl's comments are inappropriate and we are disappointed in them," he told Britain's Press Association.
"They are very uncharacteristic from Carl, who is usually a very well-behaved and measured young man.
"We are surprised and disappointed in his comments. I have spoken to his management team of Rob McCracken and Eddie Hearn and we are looking into it and will deal with it accordingly."