Okagbare won his test heat in the 100 meters yesterday and would have run the semifinals today, but is now eliminated from all competitions.
She would also have competed in the 200 meters and the ladies' relay 4x100 meters.
"The contestant was notified of the positive response and her temporary suspension this morning," the athletics anti-doping organization Athletics Integrity Unit (AIU) wrote in a statement.
"May stand in the firing line"
The sprinter belonged to the Nigerians who were allowed to compete when the AIU this week eliminated 20 other athletes from the Olympics because they were not considered to have been tested sufficiently before the games.
Ten of them came from Nigeria.
According to Inside the Games, Okagbare then accused the Nigerian federation of neglecting the competitors.
"The sports system in Nigeria is very bad and we competitors are always the ones who are allowed to stand in the firing line," she is said to have said.
32-year-old Okagbare makes his fourth Olympics and took silver in the long jump in Beijing in 2008, then after the second Russian Tatjana Lebedeva got caught for doping.
Nigeria's Olympic Committee has not commented on the doping case.
Requires retest
Just hours later, it became clear that Kenyan sprinter Mark Otieno Odhiambo will be suspended for the time being after being caught in a doping control ahead of Saturday's attempt at 100 meters, writes BBC.
The 28-year-old's test test was carried out on July 28 and showed traces of an anabolic steroid, which means that he is deleted from the starting list.
The sprinter, who showed great form before the Olympics and pulled with a personal best of 10.05 earlier in June, denies that he had any knowledge and the violation and demands that his B-test be analyzed.
Mark Otieno Odhiambo is a two-time Kenyan champion in the 100 meters and also has a first place in the 200 meters.