Austrian police suspect that the 33-year-old Alenka and the 36-year-old Mihael Kramer had managed a network of steroid dealers who had sold over the internet around EUR 38m worth of the illegal drug. The size of the network is not known.

The pair, who live in Austria's Bad Kleinkirchheim, are believed to had laundered the money through a number of shell corporations and invested it in real estate.

The Karner couple, who have been in custody in Klagenfurt since their arrest in December, are also being investigated by the Slovenian authorities for tax fraud and money laundering.

According to the General Police Administration, the international operation against the pair took place as part of Europol in cooperation with the security authorities of the US.

The investigation has shown that the criminal acts of the on-line sale of illegal performance enhancing drugs had been committed in various parts of the world, but not in Slovenia.

Silvia Strasser of the federal criminal police office from Austria's Klagenfurt explained that the arrest is based on a request from the US federal authorities, which also demanded extradition.

According to Roland Grilc, the lawyer of the Karner couple, Slovenia has not asked for extradition, but the US authorities did. He said that two conditions had to be fulfilled for extradition to the US.

The request for extradition has to contain documents proving reasonable cause for suspicion, and the mentioned act has to be regarded as a criminal act both in Austria and the US. The latter holds true, according to Grilc.

He said that Austria usually extradites suspects and charged persons if this is requested by the US, but he added that the pair is convinced that the two conditions had not been fulfilled.

The 36-year-old Gorazd Bogut, who moved to Germany with his mother as a child, was first exiled from the country in 1993, but later that year he stabbed a man in Munich a dozen times. He fled and was hiding in Croatia, but was apprehended after a few years.

Although his ten-year sentence was finished already in May 2011, state prosecutor Barbara Stockinger deemed Bogut should remain in prison under Germany's new legislative provisions on repeat offenders because he remained violent and aggressive throughout his sentence.

However, the court ruled in October against keeping Bogut behind bars and he will also receive a EUR 12,000 compensation, but he must first finish serving another three months in prison for insulting the judge at one of the hearings.

According to media reports, the Slovenian police are in contact with the German police and with all the relevant authorities in Slovenia regarding the expected return of Bogut to Slovenia by plane.

Bogut's relatives have confirmed that he will return to Slovenia and is planning on settling on his grandmother's farm in Zgornje Gradišče in northwestern Slovenia (near the border with Austria).