Chief steward Terry Bailey says he can't put a timeframe on when Racing Victoria will complete its long-running cobalt investigation.

"We are duty-bound to examine the explanations (trainers) have given us," Bailey said.

"If the explanations are right it might go a way as to whether they get charged or not.

"We keep wanting to put a time on it, but it keeps back firing.

"We've found we've had to go down different paths along the way."

Bailey was responding to an outburst from trainer Mark Kavanagh on Melbourne radio on Saturday morning.

"We've had our names tarnished. We've been named, blamed and shamed," Kavanagh told radio startion RSN.

"Syndicators have taken horses away from us because of this situation."

Kavanagh, Peter Moody, Danny O'Brien and the father-and-son training partnership of Lee and Shannon Hope, are being investigated over horses returning cobalt readings above the allowed threshold.

Insisting feed supplements are to blame for the high readings, Kavanagh says he has fully cooperated with the investigation but it has also taken a personal toll.