The news that last year's winner, Delta Blues, and runner-up, Pop Rock, will probably not travel to Australia for the Nov. 6 Melbourne Cup came as officials said Monday that the influenza may have spread to thoroughbred race horses at the Randwick track in Sydney.

More than 70 properties in two states — New South Wales and Queensland — have been affected by the outbreak, and racing has been halted in most of the country since Saturday.

Federal Agriculture Minister Peter McGauran said a national ban on all horse movements first instituted on the weekend would be extended until at least Friday. Decisions about whether weekend race meetings would go ahead would be made on Thursday, he said.

Officials are counting the costs of the suspended race meetings and to the horse breeding industry, with initial estimates placed at 1 billion Australian dollars (US$825 million, A604 million).

On Monday, investors wiped more than A$100 million (US$82.5 million, A60.4 million) off the value of major gaming companies Tabcorp Holdings Ltd., and Tattersall's Ltd., after the pair warned earnings could be impacted by the horse racing industry shut down.

Racing Victoria officials said the two Japanese horses, along with a newcomer, Tosho Knight, also had been affected by the outbreak in Japan of the influenza. Most major Japanese race meetings resumed Saturday, 10 days after the first case of horse flu was detected there.

"I haven't had any negativity from any internationals, save for the Japanese, where we do know they have issues in relation to EI (equine influenza) in that country," Racing Victoria chief executive Stephen Allanson said.

"I would have to say the contenders from Japan are extremely doubtful."

Meanwhile, four horses were found with elevated temperatures at Sydney's Randwick Racecourse but officials said they were awaiting more tests to see whether they have equine flu, said Racing New South Wales chief steward Ray Murrihy.

"In total four horses have been found with elevated temperatures," Murrihy said Monday. "Three are with one trainer but only one showed some clinical signs, the other horses were simply showing temperatures."

"We terminated training this morning and told all trainers to go into individual lockdowns until further notice."

Randwick is close to Centennial Park, where the flu was discovered in recreational horses last week. Officials said the influenza can travel up to eight kilometers (five miles) through the air to infect other horses.

The respiratory disease knocks a horse out of action for two to three weeks with a fever, hacking cough, nasal discharge and tiredness. It can be fatal in foals.

Virtually all horses exposed to the virus become sickened, making it particularly dangerous _ and costly _ for the racing community. The disease is not infectious to humans, but can be carried on clothing and spread to other horses.

No trace of equine influenza has been found in horses in New Zealand but the existence of the disease in Australia was "a huge problem" already affecting the New Zealand breeding industry, Prime Minister Helen Clark said Monday.