The US Department of Justice has stepped into the investigation around Siemens’ involvement in a slush fund scandal that is already being investigated by German prosecutors.

The corruption affair centers around the firm’s involvement in a missing Eur 200m (£132m) which, prosecutors allege, were transferred into foreign accounts and used as a slush fund for winning telecoms equipment contracts.

In a statement on its website, Siemens said: “The US Department of Justice is conducting an investigation of possible criminal violations of US law by Siemens in connection with these matters.”

It is understood the German industrial conglomerate is running its own investigation into around Euro 420m of payments, recorded as consultancy fees.

Six current or former Siemens employees, including Thomas Ganswindt, the firm’s former head of telecommunications equipment, are suspected of committing breach of trust against Siemens in cases stretching back to 2002, by setting up secret funds outside Germany.

Siemens conceded that the investigations could have a serious impact on the company. “The company’s operating activities may also be negatively affected due to imposed penalties, compensatory damages or due to the exclusion from public procurement contracts,” Siemens said on its website.

It is understood the firm’s chief executive, Klaus Kleinfeld, has hired an external anti-corruption expert to examine Siemens’ own anti-corruption safeguards.