US sprinter Erriyon Knighton given four-year ban from athletics, while Ethiopian 1500m runner Diribe Welteji cannot run until drug test case is resolved.

There were no drugs positives at all at the inaugural World Athletics Championships in Helsinki in 1983. But that was long before the creation of the Athletics Integrity Unit and the increased efforts in recent years to clean up the sport.

Less than 24 hours before the 2025 World Championship is due to begin in Tokyo, the AIU announced the news that American sprinter Erriyon Knighton has been given a four-year ban and Ethiopian 1500m runner Diribe Welteji will be unable to race the women's 1500m and 800m.

Both athletes have won medals at the World Championships in recent years with Knighton winning 200m silver in 2023 and bronze in 2022, while Welteji took 1500m silver in 2023.

Knighton, 21, who is in World Athletics' entries for the men’s 200m and is part of the US sprint relay squad in Tokyo, has been banned for four years due to testing positive for epitrenbolone – a metabolite of the steroid trenbolone – in March last year.

In June 2024 Knighton was cleared and received a “no fault violation” after an independent arbitrator ruled that the substance was more likely than not ingested through contaminated meat.

Welteji, 23, has been suspended after failure or refusal to submit a doping test last month. She was cleared by Ethiopian officials but the AIU appealed the decision and she will now be unable to race in the women’s 1500m heats on Saturday, or in any further races until the case is adjudicated.

Welteji finished runner-up behind Faith Kipyegon in the 1500m at the World Championships in Budapest two years ago and then beat Kipyegon to the inaugural world road mile title in Riga that same year.

On Knighton, the AIU said: “The Court of Arbitration for Sport (CAS) has upheld two appeals by the Athletics Integrity Unit and by the World Anti-Doping Agency against USA athlete, Erriyon Knighton, following an Anti-Doping Rule Violation (ADRV).

“Knighton has been banned for 4 years, starting from today, with credit for the provisional suspension he served between 12 April and 19 June 2024.

“The AIU appealed against the First Instance Decision of an arbitral tribunal in the USA that found that Knighton had established No Fault or Negligence for his ADRV after testing positive for a metabolite of the steroid, trenbolone in March 2024.

"Knighton had blamed his positive test on eating contaminated meat.

“As a result of the CAS decision, Knighton is not eligible to compete at the World Athletics Championships starting in Tokyo tomorrow. He was entered in the men’s 200 metres and as a member of the USA relay squad.”

The decision will almost certainly rule Knighton out of the 2028 Olympics in Los Angeles.

The Court of Arbitration of Sport (CAS) said it "has partially upheld two appeals by World Athletics and by the World Anti-doping Agency against Erriyon Knighton following an Anti-Doping Rule Violation. Knighton is sanctioned with a 4-year period of ineligibility, starting from today with credit for the provisional suspension that was served between 12 April and 19 June 2024."

CAS added: "World Athletics and WADA considered that the evidence submitted by the athlete and his explanations of a meat contamination scenario fell short of the required proof of source and were statistically impossible.

"A hearing took place on 23 and 24 June 2025 at CAS headquarters in Lausanne, Switzerland where Mr Knighton argued that the ADRV was caused by the ingestion of an oxtail dish contaminated with trenbolone.

"After considering the scientific evidence, the CAS Panel determined that there is no proof that would support the conclusion that oxtail imported into the USA would be likely to contain trenbolone residues at the level required to have caused the Athlete’s Adverse Analytical Finding."

On Welteji, the AIU said: “The Athletics Integrity Unit’s (AIU) application for provisional measures has been upheld by the CAS Division President and Ethiopian athlete, Diribe Welteji, has been suspended, pending the outcome of the AIU’s appeal to the Court of Arbitration for Sport (CAS).

“As a result, Welteji is not eligible to compete at the World Athletics Championships starting in Tokyo tomorrow, in which she was entered in the women’s 800 and 1500 metres events.

“The AIU appealed to CAS following the decision of a national hearing panel of the Ethiopian Anti-Doping Authority to clear Welteji of an Anti-Doping Rule Violation for a breach of article 2.3 of the Ethiopian National Anti-Doping Office Rules (Refusal or Failure to submit to Sample Collection).”

In a flurry of announcements on Friday evening in Tokyo, the AIU added: “The Case Management Group (CMG) of World Athletics has suspended Mike Powell (USA) indefinitely for a Safeguarding Concern, following a referral by the AIU.

"Powell is suspended from World Athletics-sanctioned activities and activities in athletics including no accreditation or credentials at World Athletics Series Events or any competitions or events organised or sanctioned by World Athletics, or any Area Association or Member Federation and no attendance (whether by invitation or otherwise) at any hospitality or other private access venue at, or in connection with, any World Athletics Series Events."