Seven Victorian racing stables, including that of top trainers Trent Busuttin and Natalie Young, have been placed in lockdown after a staff member for trainer Richard Laming returned a positive test to COVID-19.

However, Racing Victoria has stopped short of shutting down the race meeting at Moonee Valley on Saturday after its chief medical officer deemed it was safe to proceed.

RV confirmed the COVID test result on Saturday and said Laming's staff member, who has been quarantined, last worked at the Cranbourne stables on Sunday, was tested midweek and returned a positive result on Friday.

Three jockeys - Michael Walker, Jason Benbow and apprentice Alexandra Byran - have been stood down after riding work for Laming this week.

RV have undertaken contact tracing and acting on the advice of its chief medical officer, have placed seven Cranbourne stables into lockdown, including Young and Busuttin's.

Their eight horses have been scratched from the Moonee Valley and Wangaratta meetings on Saturday, while Laming and Cranbourne trainer Wendy Kelly have also withdrawn their Valley runners.

Kelly was to have saddled up smart sprinter Bons Away in the Listed Carlyon Stakes (1000m).

Both Walker and Bryan have been replaced on their rides for Saturday.

All trainers, their staff and the three jockeys will undergo testing for COVID and are required to isolate until their results are confirmed.

The Cranbourne training centre was closed for trackwork on Saturday as a precaution and will undergo a deep clean, as will Laming's stable complex.

Laming has had just one runner in the past nine days, which was at Sandown on Wednesday, and the affected staff member was not in attendance.

A decision on whether the seven Cranbourne stables and three jockeys can participate at the Ballarat and Moe race meetings during the weekend will be made on Sunday, pending the receipt of test results.