British boxer Nick Blackwell was rushed to hospital after suffering a bleed on the brain in his fight with Chris Eubank Jr on Saturday.
Widespread reports in the British media have claimed that Blackwell has been place in an induced coma.
Blackwell lost his British middleweight title to Eubank after he was stopped on medical advice in the 10th round, having taken a pummelling at the hands of his opponent, which had closed and badly swollen the area around his left eye.
The 25-year-old collapsed in the ring after the result was announced and had to be stretchered out of Wembley Arena.
"It is our understanding that Nick has a bleed on the brain and is under observation by hospital staff," British Boxing Board of Control general secretary Robert Smith told the BBC.
"We will just have to wait and see what the hospital says."
Eubank admitted after the fight: "I hit him with some big shots - maybe the referee should have stopped the fight earlier."