NAIROBI - Kenya's Daniel Wanjiru, a former London marathon champion, is the latest casualty to have failed a doping test.

Wanjiru joins a ballooning list of Kenyans who have been caught cheating as the Athletics Integrity Unit (AIU) tightens the noose. However, Wanjiru is adamant he is innocent.

AIU announced on Tuesday the provisionally suspension of Wanjiru with immediate effect after his Athlete Biological Passport showed variations, which is a violation under the World Athletics Anti-Doping Rules.

"There was a violation of Wanjiru's Athlete Biological Passport (ABP), which monitors athletes' selected biological variables over time," AIU said in a statement on Tuesday.

"In doping cases, a Provisional Suspension is mandatory under the World Athletics Anti-Doping Rules following an adverse analytical finding for any non-specified substance on the Prohibited List," it said.

However, Wanjiru in his defense said he is innocent and will prove it before AIU.

"I am clean in the sports I do. The ABP finding is confusing and frustrating me. Specialists have informed me about how this can happen and I have come to realize there can be hundreds of reasons found why HB is fluctuating. I feel I am already seen as a sinner of doping, but I am not. I am innocent. It's very painful what's happening to me now," said Wanjiru on Wednesday in Nairobi.

Though he had been running and winning marathons, Wanjiru's biggest win was in 2017 when he emerged from obscurity to beat Ethiopia's legendary runner Kenenisa Bekele to lift the London Marathon title.

He was then selected to represent Kenya at the World Championships, also in London, but he failed to shine coming home in position eight.

This year alone, Kenya has also seen former world marathon record holder Wilson Kipsang, Kenneth Kipkemoi, Mercy Jerotich, James Kibet and former world junior 800m champion Alfred Kipketer suspended and charged for whereabout failures by AIU.

"A provisional suspension may be imposed in other doping cases depending on the nature and circumstances of the case in question," AIU said.

In 2018, Wanjiru finished eighth in London marathon and last year was in position 11 in a race won by compatriot Eliud Kipchoge.

"I have always believed that those athletes, who are suspended because of a doping violation, were indeed guilty of what they did. But I have realized that being charged of guilt is just easy and now proving being not guilty is hard," Wanjiru said. "I stand for clean sports. My results of the past came through hard work only. I have never used doping. We are currently investigating the case."