The International Rugby Board has confirmed testing for the designer steroid THG will begin at the World Cup early next week.

The tournament's move to test for Tetrahydrogestrinone (THG) comes after news earlier this week that British sprinter Dwain Chambers tested positive to the substance.

Previously undetectable, THG is regarded as a powerful steroid that aids recovery and boosts strength.

Methods for testing THG had been passed on to major sporting bodies over the last week in a bid to ensure the substance could be picked up in athletes as soon as possible.

RWC anti-doping manager Tim Ricketts confirmed that testing for THG would start early next week and said there was a good chance prior samples taken from rugby players before, and during, the early stages of the tournament would be re-tested.

"As soon as the laboratory in Sydney is ready to go with it they'll begin," he said.

"They are just fine-tuning the methods and analysis techniques to test for the drug.

"We are saying the testing may extend back to samples already taken. We are looking into that further.

"There are issues we need to look into, such as the integrity and security issues over samples already taken."

Prior to the tournament 105 players were drug tested.

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