The AIU, which is an independent integrity body created by the World Athletics, disclosed this in a statement on Saturday.
The growth hormone is a non-specified substance on the 2021 World Anti-Doping Agency (WADA) Prohibited List.
A provisional suspension is mandatory following an adverse analytical finding for such substance under the World Athletics Anti-Doping Rules.
The AIU collected the sample from Okagbare during an out-of-competition test on July 19.
The WADA-accredited laboratory which analysed the sample notified the AIU of the adverse analytical finding at mid-day Central European Time on Friday.
AIU said the athlete was notified of the adverse analytical finding and of her provisional suspension Saturday morning in Tokyo.
She was scheduled to participate in the semi-finals of the women’s 100m Saturday evening.
The AIU said it would make no further comment on the matter at this time.
Okagbare had on Friday cruised to first place in her 100m heat in 11.05 seconds to qualify for Saturday’s semi-finals at the Tokyo Olympics.
She was also due to compete in the 200m, as well as the 4x100m relay.
The 32-year-old medal prospect for Nigeria won silver in the long jump at Beijing 2008 Olympics.
At the 2013 World Championships in Moscow, she won long jump silver and 100m bronze, while she won the 100m/200m double at the Glasgow 2014 Commonwealth Games.
She is competing in her fourth Olympics for Nigeria.