He tested positive for nandrolone in an out-of-competition test in the Olympic village.

Jacobs was most recently given an out-of-competition test on July 23, and she passed, Williams said.

Clarke, a 34-year-old, tested positive for the steroid stanozolol in a random out-of-competition test on July 31.

Grimes failed an out-of-competition test administered by track and field's world governing body, a person with knowledge of the test said.

She received a four-year ban from athletics after failing a drugs test, having been positive for steroids in an out-of-competition test.

Last year alone, he was given eight urine tests, including one out-of-competition test, as well as a blood test.

Unannounced, out-of-competition tests are considered the only reliable way to catch cheaters.

The sample containing the banned substance was delivered on 27 March 2006 in an out-of-competition test.

In 2005 she tested positive for a banned substance in an out-of-competition test.

There will also be a dramatic increase in random, out-of-competition tests.