Prisoners at a high-security Bosnian jail are suspected of using a carrier pigeon to smuggle in drugs, a senior prison official said on Thursday.
"We are investigating the case after four convicts tested positive for drugs," Josip Pojavnik, deputy warden of Zenica prison, told Reuters by telephone.
Officials were tipped off that four convicts who looked after a pigeon-house in the courtyard might have trained birds to carry drugs.
However, an initial investigation pointed to a bird trained outside prison as the carrier of heroin and cocaine in small bags attached to its legs, Pojavnik said.
He added that police were investigating a pigeon-owner who is not behind bars.
Prisoners in Zenica serve sentences for serious crimes such as murder, drug dealing, war crimes and crimes against humanity. Amnesty International has complained in the past about conditions at the prison.
Reporting by Daria Sito-Sucic, editing by Andrew Dobbie