Blackwell needed an emergency procedure to reduce brain swelling following an unsanctioned sparring session.
The 26-year-old retired from boxing earlier this year after he had to be put into an induced coma following a defeat by Chris Eubank Jr.
Blackwell remains stable in hospital but is yet to regain consciousness.
The former British middleweight champion is no longer being sedated, but he had a section of his skull removed to ease swelling on his brain. His recovery time and prognosis remain unclear.
The BBBofC's initial investigation has found that Blackwell was involved in a gym sparring session with a licenced boxer on 22 November.
BBC Wales Sport understand he is a professional fighter rather than an amateur.
Blackwell complained of headaches after the sparring session and was taken to hospital where it was determined surgery was necessary.
BBBofC secretary Robert Smith told BBC Wales Sport: "We are calling people we know were involved and we are calling people we believe were involved.
"We are looking at arranging a hearing that will happen early in January. It is a matter we are taking extremely seriously.
"We want to hear from Nick as well, health permitting."
Smith said the board would not yet discuss possible sanctions against those involved, although promoter Frank Warren has called for them to have their licences revoked.
"We will wait and see what happens at the hearing, I don't want to speculate on possible punishment," Smith added.
Blackwell's former trainer Gary Lockett, who was unaware Blackwell was sparring, says he is facing a long road to recovery.
"This is not a quick process, we are looking at several months," he said.
Lockett has called on the people who let Blackwell spar to be banned from the sport.
"I can't believe the boxer he sparred with, and the coach or coaches involved, would ever allow Nick to spar when he's had a brain injury," Lockett told BBC Radio Wales.
"In due course, I hope they are dealt with by the British Boxing Board of Control in the correct manner."
A hearing into the circumstances that led to Nick Blackwell undergoing brain surgery will be held in January, the British Boxing Board of Control says.