An arbitration panel hearing world champion sprinter Torri Edwards's doping case has determined there may be "exceptional circumstances" for her positive stimulant test and has referred the case to the IAAF, her agent-lawyer told Reuters on Thursday.

"We are pleased the arbitration panel agreed that she is not a cheat," Emanuel Hudson said in a telephone interview from his southern California office.

But he cautioned that this was "just another hurdle" for Edwards as she fights to retain her place in next month's Olympics.

The case now goes before an IAAF (International Association of Athletics Federations) doping review board, Hudson said.

If it disagrees it would seek a two-year ban for Edwards.

A lesser penalty, or no penalty, could result if the board accepts the arbitration panel's decision.

Edwards is considered a medal contender in the women's 100 and 200 metres and 4x100 metres relay at next month's Games.

The 27-year-old tested positive for the banned stimulant nikethamide at an April meeting in Martinique. She contends she was given glucose tablets by her physical therapist, who did not know they contained the drug.

Edwards could appeal against any IAAF decision to the Swiss-based Court of Arbitration for Sport (CAS).

Hudson said he hoped the case would not go that far but added Edwards would not race until the Olympic Games to ensure she would be available for any additional hearings required.

Edwards finished second in the 100 metres and third in the 200 metres at this month's U.S. Olympic trials. She gained the world 100 metres title this spring when fellow American Kelli White admitted using banned drugs.