NAIROBI, Kenya (AP) — Former Olympic 1500-meter champion Asbel Kiprop says he has tested positive for doping and is alleging officials gave prior warning of the supposedly unannounced out-of-competition test before extorting money from him.

Kiprop wired funds to one of the doping control officers while they were at his house in Iten, Kenya, collecting his urine sample last November, he said in a statement issued via his lawyer on Thursday.

The 2008 Olympic gold medalist and three-time world champion said he learned in February the sample tested positive and was "extremely shocked."

"I vehemently deny any doping," he said.

News of the failed test was first reported on Wednesday by the UK's Daily Mail newspaper. The IAAF anti-doping unit would not comment on the report on Thursday.

Out-of-competition tests are meant to be a surprise for athletes, to maximize the chances of catching cheats and to leave them no time to flush any banned substances out of their system.

Kiprop, however, said one of the testers told him the day before to be ready for the Nov. 27 test and then, after collecting his sample, asked for money.

The athlete said he wired funds via mobile phone but did not say how much.

"At that time I did not see the money as inducement or bribe for anything," Kiprop said. "In retrospect I now clearly see the money as having a relation with the sample collected on that date, and even the irregular advance notice I was given.

"I remain perplexed on how my innocent sample could turn positive the only time when money was extorted from me. It is not beyond my suspicion that my sample turned positive because I might have remitted less money than I was expected to remit."

Kiprop's statement did not specify what substance he tested positive for.

However, he appeared to suggest it might be the banned blood-boosting hormone EPO, saying: "I am told EPO is put into the body using injection. The last time I had an injection was in 2014 when I was given a yellow fever vaccination before travelling to the Bahamas for a competition."

Kiprop's failed test deals another damaging blow to Kenya's reputation as a middle and long-distance running superpower.

Dozens of Kenyans have tested positive for an array of doping substances in recent years. They include big-name athletes, among them Olympic marathon champion Jemima Sumgong.

Like four other elite Kenyan runners who also failed doping tests, Kiprop worked with Italian agent Federico Rosa. The others are Sumgong, Rita Jeptoo, Matthew Kisorio and Agatha Jeruto.

Sumgong and Jeptoo tested positive for EPO and were banned for four years. Kisorio and Jeruto tested positive for traces of steroids and were banned for two and four years respectively.

Rosa said he was "shocked" by the news of Kiprop's failed test.

"It is very, very strange to me after so many years of such an incredible career," Rosa told The Associated Press in a phone interview.

Rosa said he was traveling when the story broke and that he has since been trying unsuccessfully to speak to his athlete.

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AP Sports Writer John Leicester in Paris contributed to this report.