Blessing Okagbare has been handed a 10-year ban for breaching doping regulations, while Great Britain have lost Tokyo 2020 Olympic silver medals after CJ Ujah tested positive for a banned substance.

Nigerian track and field athlete Okagbare, who specialises in long jump and short sprints, is an Olympic and World Championship medallist, including silver in Beijing in 2008.

The 33-year-old also won her heat at the Tokyo Olympics in the women's 100m, but a positive test for a human growth hormone in July ruled her out of the semi-finals at the Games.

The Athletics Integrity Unit (AIU) has now acted by banning Okagbare for 10 years after positive tests for multiple substances and failure to cooperate with investigations.

An AIU statement on Friday read: "The Disciplinary Tribunal has banned Nigerian sprinter Blessing Okagbare for a total of 10 years, five years for the presence and use of multiple prohibited substances and five years for her refusal to co-operate with the AIU's investigation into her case.

"The sole arbitrator adjudicating the case concluded that the athlete's use of multiple prohibited substances as part of an organised doping regimen in the lead up to the Tokyo Olympic Games was egregious conduct that amounted to aggravating circumstances under the Rules thereby warranting an additional period of ineligibility on top of the standard four-year sanction.

"The sole arbitrator also recognised the AIU's right to carry out investigations, including the imaging of electronic devices, and to impose sanctions when an athlete refuses to co-operate with an investigation and thereby frustrates the AI's ability to fulfil its mandate to protect the integrity of the sport of athletics.

"In this instance, the sole arbitrator concluded that the athlete's refusal to cooperate had denied the AIU the opportunity to discover evidence of possible further rule violations by her as well possible violations of the rules by others, for which he imposed an additional sanction of five years."

Head of the AIU Brett Clothier added: "We welcome the decision of the Disciplinary Tribunal; a ban of 10-years is a strong message against intentional and coordinated attempts to cheat at the very highest level of our sport."

On the same day, Great Britain were stripped of their silver medal in the men's 4x100m relay at the 2020 Games after Ujah's drug test returned traces of ostarine and S-23 – both banned substances.

Ujah raced in the first leg of the sprint relay as Great Britain, with a team also including Zharnel Hughes, Richard Kilty and Nethaneel Mitchell-Blake, edged out Italy for second on the podium.

The Anti-Doping Division of the Court of Arbitration for Sport (CAS ADD) stated that Ujah had "not knowingly or intentionally doped, suggesting that the source of the prohibited substances could have been the ingestion of a contaminated supplement."

The statement added: "The CAS ADD sole arbitrator issued the present decision in which she determined, to her comfortable satisfaction, that an anti-doping rule violation had been committed."

The CAS ADD said that it has requested World Athletics to consider further action against Ujah within their jurisdiction, including on whether a ban may be imposed.

Ujah reiterated in his statement that he had not knowingly "consumed a contaminated supplement and this was the reason why an anti-doping rule violation occurred at the Tokyo Olympic Games."

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In his statement, he continued: "I sincerely regret that this has inadvertently led to the forfeiture of the men's 4x100m relay team's Olympic silver medals at the Tokyo Olympic Games.

"I would like to apologise to my teammates, their families and support teams for the impact which this has had on them.

"I'm sorry that this situation has cost my teammates the medals they worked so hard and so long for, and which they richly deserved. That is something I will regret for the rest of my life."

He added that representing Team GB "surpassed my childhood ambitions and I will forever be devastated that this situation has marred the success achieved" in Tokyo.

"I would also like to apologise to both British Athletics and Team GB. British Athletics has supported the relay athletes for years and this has been difficult for everyone involved in the programme."