Duisburg, Germany - German state prosecutors' hands remain tied over a Mafia killing spree at a German pizzeria 18 months ago, German Spiegel magazine reported Saturday. The legal team in the city of Duisburg said they had refused the extradition to Germany of the prime suspect, Giovanni Strangio, who was arrested in Amsterdam last month, as they lacked evidence to proceed in court against the him.

Next week, a Dutch court is to formally decide whether 30-year-old Strangio should be extradited to Italy or Germany.

One and a half years after six members of an Italian Mafia clan were murdered in the western German city of Duisburg, German investigators are struggling with the lack of cooperation with their Dutch and Italian counterparts, Spiegel reported.

Both countries had failed to respond to requests for legal assistance, and the German investigators had not yet received a saliva sample needed for identification purposes.

One of the investigators, who wished to remain anonymous, told Spiegel the investigation marked a "low point in the fight against organized crime in Europe."

Strangio, 30, was arrested in March after a lengthy probe involving telephone wire tapping, surveillance and close coordination between Dutch, German and Italian police.

At the time police also captured Strangio's brother-in-law Francesco Romeo, who is thought to have assisted in the murders.

Another brother-in-law, who was also accused in the Duisburg murders of rivals in the southern Italian criminal organization 'Ndrangheta, was arrested in November, also in Amsterdam.

Giuseppe Nirta, a senior leader of 'Ndrangheta, had been sought by Italy for more than a decade to serve a sentence of nearly 15 years for drug trafficking.

The German shootings were the climax of a feud between the Nirta-Strangio and Pelle-Vottari clans that had already cost several lives in the mob's home base of Calabria. (dpa)