Racehorses stabled at two Sydney tracks have been targeted in a series of random doping tests for a performance-enhancing drug better-known for its use in the world of cycling.Racing NSW stewards confirmed on Monday they made surprise visits to stables at Warwick Farm and Randwick and tested 100 horses for Erythropoietin (EPO).Stewards made unannounced visits to Randwick stables on Monday after turning up at Warwick Farm last Wednesday.Chief steward Ray Murrihy said a total of 25 stables were in

Racehorses stabled at two Sydney tracks have been targeted in a series of random doping tests for a performance-enhancing drug better-known for its use in the world of cycling.

Racing NSW stewards confirmed on Monday they made surprise visits to stables at Warwick Farm and Randwick and tested 100 horses for Erythropoietin (EPO).

Stewards made unannounced visits to Randwick stables on Monday after turning up at Warwick Farm last Wednesday.

Chief steward Ray Murrihy said a total of 25 stables were involved in the operation.

Samples taken from Warwick Farm-stabled horses have been cleared after being tested by the Australian Racing Forensic Laboratory (ARFL).

Analysis of the Randwick tests took place late Monday and the results are expected on Tuesday.

Murrihy said concerns raised about the use of EPO in Victoria during the spring carnival had prompted NSW to upgrade its testing procedures against the banned substance.

"The Melbourne authorities did articulate some concerns about EPO there and we need to be alive to those possibilities here as well," he said.

"We don't have any intelligence to suggest there is any evidence that EPO was being used in Melbourne but what we are doing is seeking better intelligence to whether there is any EPO out there in NSW.

"We have also sought assistance from a number of government regulatory agencies to see if there is any leakage of any EPO products away from hospitals or any misuse in the veterinary profession."

Murrihy said part of the revised strategy against the possible use of EPO was to have more out-of-competition testing for the drug.

"We feel that our resources should be directed into unannounced stable visits, trials and those sorts of venues at metropolitan, provincial and country racetracks," he said.

EPO is released from the kidneys and acts on the bone marrow to stimulate red blood cell production, according to the Australian Sports Anti-Doping Authority (ASADA).

It says an increase in red blood cells improves the amount of oxygen the blood can carry to the body's muscles and it may also increase the body's capacity to buffer lactic acid.

Breakthrough testing by a French laboratory found four stage winners in this year's Tour de France had used an advanced form of EPO.

Among the cyclists exposed was Austria's Bernhard Kohl, the best climber in this year's race.

Because of the new analytical procedures, the International Olympic Committee will retest frozen blood samples taken from athletes during the Beijing Games.