Former world number one Martina Hingis announced that she has tested positive for cocaine during this year's Wimbledon tournament.

The Swiss Hingis was expected to announce her retirement from professional tennis for a second time, after struggling to recover from a string of injuries and health problems.

Hingis, 27, called an early end to her season last month following difficulties with her hip, saying she would take "as much time as it needs to get fully fit again".

The Swiss media has subsequently been full of reports that the five-time Grand Slam champion was set to hang up her racket for good.

But instead she issued a shock statement that she had tested positive for the drug during this year's disappointing All England Club visit, when she lost in the third round to unseeded American Laura Granville.

The Czech-born Swiss, who won many fans for her graceful and tactical style of tennis, first announced her retirement in 2003 after failing to overcome a series of ankle injuries.

Following her return to the tour, Hingis surprised her doubters by winning three more titles and ending 2006 as the world number seven.

Even with her current injury problems, she is ranked 19th in the world.

Reuters