The Birmingham-based boxer, who had been tipped to take the gold medal in Beijing, was forced to pull out of the Games just a day before it began after he came in 1.36kg over his 60kg mark for the lightweight division.
Amateur Boxing Association (ABAE) chief executive Paul King admitted Gavin's withdrawal was a huge disappointment on the eve of the Games and an internal investigation would now be held.
He said: "ABAE will launch an internal investigation into the circumstances leading up to (Gavin's) withdrawal, which is a massive blow to our gold medal hopes, and to our essential UK Sport and lottery funding."
The 22-year-old is reported to have benefited from Lottery funding worth around £70,000 a year in the run-up to the Olympics which funded his training programme and included coaching, sports medical expertise and dietary advice.
GB boxing coach Terry Edwards defended his decision to pull Gavin out, saying it was the 'hardest decision he had ever had to make in boxing'.
"I felt if I pushed it any further there would have been a serious health risk," he said.