Nick Blackwell, who fell into a coma after a loss to Chris Eubank Jr. in March, is back in the hospital after he underwent surgery following a sparring session, prompting the British Boxing Board of Control to launch an investigation, according to The Daily Telegraph.

The 26-year-old middleweight retired from the sport after he was stopped in the tenth round and collapsed in the ring against Eubank on March 26 at Wembley Arena. He spent nine days in a medically-induced coma after sustaining bleeding on the skull and was subsequently stripped of his license to compete by the British Boxing Board of Control.

However, Blackwell reportedly took part in a sparring session on Nov. 22 despite the health scare, according to BBC.com. Blackwell suffered additional swelling on the brain and required surgery after the sparring session, according to the BBC.com. He is thought to be in stable condition.

“I couldn’t believe Nick would be so stupid as to put his health at risk,” Blackwell’s former trainer Gary Lockett told BBC.com. “I can’t believe the boxer he sparred with, and coach or coaches involved, would ever allow Nick to spar when he’s had a brain injury. In due course, I hope they are dealt with by the British Boxing Board of Control in the correct manner.”

British Boxing Board of Control secretary Robert Smith plans to launch a probe into the circumstances surrounding the sparring session. Blackwell was attempting to transition to the role of trainer and was set to help work the corner of Liam Williams’ bout this past Saturday against Gabor Gorbics.

“What we understand is that Nick Blackwell sparred, he was taken ill and taken to hospital where he is in a stable condition,” Smith told the Telegraph. “He no longer has a boxer’s license, but he does have a trainer’s license, which is a completely different thing. He should not have been boxing. I’m sickened by it. It’s a very tough sport and the doctors here did a wonderful job to save his life.”