"Visitors to the U.K. are able to travel the country without restrictions, so providing Olympic athletes have a valid visa at the moment, it would be premature to suggest that any have absconded," said Carlos Vargas-Silva, a senior researcher at the Migration Observatory at Oxford University.
But he said it is difficult to track people who decide to overstay their visas.
Donna Covey, the Refugee Council's chief executive, said that Britain must protect people who can prove they need shelter from conflict because it has signed the 1951 U.N. Refugee Convention.
"It's a tragic fact that many people competing in the Olympics come from countries around the world where they are at risk of human rights abuses, conflict and violence," she said. "Over the last two weeks, we welcomed the world to the U.K. for the Olympics, so we must now also uphold our proud tradition of offering safety to those fleeing persecution."
Associated Press writers Robbie Corey-Boulet in Abidjan, Ivory Coast, and Boubacar Diallo in Conakry, Guinea, contributed to this report.
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