Berlin-based company Vero is suspected of having smuggled material to build the nuclear reactor through Poland to Moscow, from where it was taken to Iran, said Christoph Lange from the prosecutor's office in Potsdam near Berlin.

He said Vero appeared to have been buying up nuclear technology in Germany and elsewhere in Europe since 2000 at the orders of Russia, which is constructing Iran's first nuclear power plant in the town of Bushehr.

Lange said prosecutors have so far only traced material worth about five million euros (6.8 million dollars), but that this appeared to be the tip of the iceberg. Up to 150 million euros' worth of material may have left Germany for Iran, he estimates.

The companies being probed have claimed that the material was destined for Russia but at least a dozen of them must have known that Iran was the final destination, Lange said.

Only one of the companies under investigation is seated in the former communist East Germany. It is believed to have exported parts for a crane meant to be used in the Bushehr reactor to Russia in 2001 and 2002.

In 2004, a company employee was arrested in the east German state of Saxony-Anhalt on suspicion of smuggling technology destined for Iran to Russia.

Russia said earlier this month that the Bushehr plant will not be completed before 2008.

The project has been hit by a series of delays and financial difficulties, which has seen Russia and Moscow accuse each other of not living up to their obligations.

Iranian officials have charged that Russia is being half-hearted in finishing the project at a time when the United States is calling for more sanctions over Tehran's refusal to halt uranium enrichment, which is the central issue in the international standoff over Iran's nuclear programme.

Washington accuses Tehran of trying to make nuclear weapons but the hardline Islamic state insists it is running a peaceful nuclear programme solely aimed at meeting its civilian energy needs.

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