Hoeness is accused of hiding millions of euros from tax authorities in a Swiss account and is due to go on trial at Munich's higher regional court on March 10.

The 62-year-old is said to have been threatened by both email and post, but the email account was a fake and the letter he received could not be traced when the matter was investigated.

"The perpetrators could not be identified," a spokesman for Munich's prosecution service told SID, an AFP subsidiary.

Hoeness, a 1974 World Cup winner with West Germany, has vowed to prove his innocence in court having been arrested last March and released on bail.

On Thursday, a Bavarian tax office was raided by officials as part of the investigation into Hoeness' affairs.

Munich prosecutors were looking to find who had access to a tax document from Hoeness which was eventually printed in German magazine Stern.