An international law firm has been appointed to investigate claims of bribery after an internal probe by Siemens, one of Germany's largest companies, failed to produce results.

Dozens of Siemens staff members have been giving evidence in the probe, providing information on the amounts paid to Greek officials in various fields, not just telecommunications.

Kickbacks are believed to have been given to Greek political parties, particularly before the 2004 national elections, OTE telecom staff members and officials involved in the construction of Olympic Games venues worth billions of euros.

Four of the staff members questioned are also believed to have given evidence of bribes in connection to Greece.

Munich-based Siemens is being investigated worldwide on corruption allegations and could face high fines in the United States or even be banned from public contracts there.

The scandal has already cost the 160-year-old company 1.6 billion euros and led to the resignation of two senior company officials.

The US Securities and Exchange Commission is investigating whether employees of Siemens, one of the world's largest electrical and industrial engineering companies, paid hundreds of millions of euros in bribes for telecommunications and other contracts.

The largest amount of suspect payments outside Germany had been made in Austria, according to Siemens Chief Financial Officer Joe Kaeser.