Atef Chaloub, a member of the National Olympic and Sports Committee of Guinea (CNOSG), told Reuters that swimmer Amadou Camara and judoka Mame Adama Bangoura stayed in Brazil.

"They didn't come back with us," he said.

It is possible they have become illegal economic migrants, continuing a trend of African athletes going abroad for Olympic competition and remaining in the host country.

More than a dozen athletes from Cameroon, Eritrea, Guinea and the Ivory Coast went missing from the London 2012 Athletes’ Village.

Weynay Ghebresilasie, the steeplechaser who carried Eritrea's flag during the London 2012 Opening Ceremony, was one of the few who came out of hiding to admit he was seeking asylum to escape from a repressive regime back home.

Meanwhile, five missing Cameroon boxers turned up to train at a gym in South London before disappearing again.

It was reported the following year that two of them, Thomas Essomba and Blaise Yepmou Mendouo, had been granted asylum by the Home Office and sent to Sunderland.

At the Manchester 2002 Commonwealth Games, 20 members of the Sierra Leone team went missing from their camp before the end of the competition.

Visa overstays and asylum applications also followed the Sydney 2000 Olympics, while Olympic defections were common during the Cold War.

One of the best-known incidents was at the Melbourne 1956 Olympics when half of the Hungarian delegation defected to the West after the Games.