Twenty-one year-old Grace Nwokocha is reported to have returned a positive result for anabolic steroids in her A sample. The drug was not named.
Nwokocha, who was also fifth in the women's 100m, anchored the relay team that included Tobi Amusan, Rosemary Chukwuma and Favor Ofil as they secured an African record 42.10 seconds.
England, who finished second in 42.41, would be upgraded to the gold if the allegations are proven to be true. The Jamaicans, who clocked 43.08, would take silver while Australia, who had finished fourth in 43.16, would get bronze.
Elaine Thompson-Herah, who won the sprint double at the games, ran a blazing anchor leg to snatch third for Jamaica, with Kemba Nelson, Natalliah Whyte and Remona Burchell also making up the team for the final.
Reports in the media are that World Anti-Doping Agency (WADA) has informed the Athletics Federation of Nigeria (AFN) of the development while still awaiting confirmation of the B sample.
