Six racing pigeons in Belgium were found to have been doped with drugs such as cocaine and painkillers, newspapers in the country say.
They said that the doping was revealed when the Belgian pigeon-racing federation sent samples from 20 birds to the National Horseracing Authority of Southern Africa.
The newspapers said that the birds tested positive for numerous drugs.
Pigeon racing in Belgium is a highly lucrative sport.
In May a Belgian racing pigeon called Bolt - named after Olympic gold-winning Jamaican sprinter Usain Bolt - was sold to a Chinese businessman for a world record price of 310,000 euros (£260,000: $400,000).
It was thought that the buyer wanted to use Bolt for breeding more birds.
Correspondents say that the riches and glamour connected with racing pigeons have brought many problems, including thefts from breeders and racketeering.
Reports say that the doping of the birds was only unearthed in South Africa - tests carried out in Belgium did not reveal a problem.
The sport revolves around specially bred and trained pigeons released from a specific location and racing back to their home loft.