About 4,000 rare imported chickens being held in quarantine in Adelaide could be destroyed as soon as Friday.

The Federal Agriculture Department, which issued a destruction order after one chick returned a positive result to salmonella, says the birds will be euthanased "soon".

The Australian Rare Poultry Importation Syndicate, which discontinued Federal Court action against the destruction, said it believed the chickens were to be destroyed on Friday.

The syndicate of about 80 people spent $500,000 importing 45 breeds from the United Kingdom in an attempt to restock Australia's poultry breeds.

The eggs hatched in incubators two months ago and the chickens are being held in quarantine on Torrens Island off Adelaide.

After a destruction order was issued, the syndicate was granted an injunction to give them more time to conduct tests, but three more chickens have since tested positive to salmonella.

Lawyers for the syndicate have now discontinued their court action, saying it accepted the department's decision was validly made.

The injunction, which was to expire at midnight, was also discharged.

In a statement, the Department of Agriculture, Fisheries and Forestry (DAFF) says the chickens are infected with an exotic strain of salmonella that cannot be effectively treated.

"The Federal Court of Australia's injunction has been removed today and DAFF will start to destroy the flock under veterinary supervision soon.

"While the decision to destroy the flock is unfortunate, it is an example of Australia's biosecurity system working.

"All animals imported into Australia are subject to rigorous health and quarantine checks in accordance with strict import conditions.

"The purpose of a quarantine facility is to detect, manage and prevent the escape of exotic pests or diseases into Australia."