Jones had until March to begin her term in prison

Jones, 32, pleaded guilty to lying about steroid use and involvement in a drugs fraud case last October.

She reported to the Federal Medical Center-Carswell in Fort Worth just before noon, said prisons spokeswoman Traci Billingsley.

The mother of two was stripped of five Olympic medals and has retired.

When sentenced in January, Jones was given until 11 March to begin her jail term.

Spectacular fall

She will also serve two years' probation for lying to federal investigators about her use of performance-enhancing drugs and about a cheque fraud case involving her former boyfriend, sprinter Tim Montgomery.

Once arguably the most famous female athlete in the world, Jones won gold in the 100m, 200m and 4x400m relay as well as bronzes in the long jump and 4x100m relay, at the Sydney Olympics in 2000.

But she suffered a spectacular fall from glory last October, when she admitted using a steroid between September 2000 and July 2001.

At her sentencing, a tearful Jones said she was "deeply sorry" for her offence, and said she hoped "that people will learn from my mistakes".