Hingis quits following positive cocaine test

Tennis ace Martina Hingis is under investigation after testing positive for cocaine.

The 27-year-old Swiss player announced her retirement from the sport on Thursday after admitting she failed a drugs test at the Wimbledon tennis championships in England earlier this year.

Hingis, who has endured a string of ankle injury problems in recent years, insists she has never used cocaine.

She says: "I have tested positive but I have never taken drugs and I feel 100% innocent.

"The reason I have come out with this is because I do not want to have a fight with anti-doping authorities.

"Because of my age and my health problems, I have also decided to retire from professional tennis."

Hingis won five Grand Slam titles during her career. She retired from tennis in 2003 due to her ankle, but re-emerged in 2006 before being forced to prematurely end her season again last month due to hip problems.