Authorities in Victoria saying no cases of Equine Influenza (EI) have been detected in the state.
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But the national lockdown on horses has been extended to 1pm AEST on Friday.
The outbreak affected hundreds of horses on 68 properties in New South Wales, and two in Queensland.
"All horses that have been brought into Victoria over the last 14 days have been tested and there's no evidence of any of this virus being present," Racing Victoria Limited (RVL) chairman Graham Duff said.
"Victoria still has no incidence of the equine influenza epidemic that is evident in NSW."
Mr Duff said permits would now be sought to allow horses to leave their stables and resume training at the Flemington and Caulfield racecourses.
The Melbourne spring carnival is the biggest in the country and there were fears Australia's iconic race, the Melbourne Cup might have to be moved.
But the international participation is still in doubt.
Japanese Delta Blues and Pop Rock, who were first and second in last year's Melbourne Cup, were yesterday ruled out of the spring carnival.
They hab been unable to enter quarantine in Japan where there is also an equine flu outbreak.
Leading betting agencies around the country have suspended betting indefinitely on the Caulfield and Melbourne Cups.
The economic impact is already in the tens of millions of dollars after three days without racing, although events in Queensland and South Australia are expected to resume along with Victoria this weekend.
The racing industry depends on income from Tabcorp wagering to exist and around $40 to $50 million has been lost over the past three days, with more to be lost if Queensland and NSW races are cancelled.
Randwick tests negative
Meanwhile four thoroughbred racehorses stabled at the Randwick track and suspected of having equine influenza have tested negative to the virus.
Racing NSW chief executive Peter V'Landys said the results were a relief but caution should still be exercised.
"It is good news but it is just the first hurdle," V'Landys said.
"So far no racehorses have tested positive but a lot of areas will remain locked down until this burns itself out."
Tests will confirm today whether 300 horses quarantined west of Brisbane have been exposed to horse flu.
The horses have been contained at Warwick's Morgan Park since the weekend after four horses at an equestrian world cup qualifier there showed symptoms.
Calls for inquiry
Racing officials and politicians have called for an inquiry into Australian quarantine procedures following the country's first outbreak of EI in a stallion at the Eastern Creek quarantine centre last Thursday.
"Whatever happens we urge both governments to take internal control audits of these quarantine stations and ensure that the chemicals they are using to wash out the horse floats are the latest and best,” Mr V'Landys said.
"Someone has been negligent."
Opposition Leader Kevin Rudd said Australia needed to know how the outbreak occurred.
"I believe there needs to be an urgent and independent inquiry as to whether there has been any breakdown in Australia's quarantine procedures, because the impact for Australia's equine industry is so huge," Mr Rudd said.