Authorities have responded to criticism they have been slow to act against former BC3 chairman Bill Vlahos, saying the investigation is the most complex ever undertaken by Racing Victoria.

BC3 Thoroughbreds collapsed in December and Vlahos declared bankruptcy in the middle of a NSW Supreme Court case into a supposed punting club he ran separately from the racing concern.

Dayle Brown, the head of RV's integrity services, said the investigation was complex but nearing completion.

"We have gathered over one million pieces of data during the course of our investigation and have had forensic IT and financial experts working alongside our investigators to analyse it," Brown said.

"The analysis of this data has taken considerable time, but we are nearing completion of this phase of the investigation and are building an intimate picture of BC3 Thoroughbreds and its racehorse ownership business.

"Mr Vlahos is central to our investigation into BC3 Thoroughbreds and we are continuing to examine the evidence obtained regarding his activities as chairman of the company.

"As it stands, any horses owned by Mr Vlahos or BC3 Thoroughbreds are subject to the jurisdiction of the bankruptcy trustee or company administrator so he derives no benefit if they compete."

Vlahos did not attend a meeting of creditors in Melbourne last Friday.

Brown said two investigators were working full time on the complex case.

"We are keen to complete this investigation as swiftly as possible, but it's important that people understand the magnitude and complexity of the work being undertaken," Brown said.

"We will bring this investigation to its conclusion as soon as possible without compromising the outcome."

He said evidence needed to be collected to substantiate any charge which might be brought against any individual.

Vlahos made national headlines at last year's Easter Yearling Sale when he bid a record $5 million for a half brother to Black Caviar.

BC3 defaulted on payment for the colt who was euthanised in December after a long battle with the deadly hoof disease laminitis.