Okagbare tested positive for human growth hormone in an out-of-competition test on July 19, four days before the Olympics opened, the Athletics Integrity Unit (AIU) said, prompting a mandatory provisional suspension.
The AIU informed Okagbare of her suspension on Saturday morning, it said, ruling her out of the 100 metres and likely ending her Olympic campaign.
Under doping regulations, she is allowed to request that a “B” sample – or backup sample – is tested to double-check the results.
The 32-year-old Okagbare won a silver medal in the long jump at the 2008 Beijing Olympics and at the 2013 World Championships.
She also collected a bronze in the 200 metres at the 2013 World Championship in Moscow behind Shelly-Ann Fraser-Pryce, who is the favourite for the 100 metres title in Tokyo. Okagbare did the 100-200 double at the 2014 Commonwealth Games.
Okagbare’s suspension came three days after the AIU announced that 10 track and field athletes from Nigeria were among a group of 20 from various countries who were disqualified from competing at the Olympics because they had not met minimum doping test requirements.
The AIU did not name any of those athletes.
Nigeria is considered a high-risk country by the AIU because of a brittle anti-doping programme. Because of that, Nigerian athletes must have at least three out-of-competition tests in the 10 months before a major championship.
Nigeria was moved into the high-risk category last year when the problems with its anti-doping programme were described as “very serious” by AIU Chairman David Howman.
Some Nigerian athletes who said they were among those barred from the Olympics by the AIU protested on the streets of Tokyo this week. They held up signs claiming Nigerian sports and anti-doping authorities were responsible for them not meeting the testing criteria.
Kenya dropped two runners from its Olympic team just before the Tokyo Games opened because they had not undergone enough out-of-competition tests in the buildup to the Olympics.