German referee Robert Hoyzer fixed or attempted to fix a total of seven matches as part of the country's biggest soccer corruption case in over 30 years, says the German Football Association.

"We are talking about organised crime here," Bundesliga chief Werner Hackmann told a news conference, called on Thursday after German football chiefs had studied evidence given to them by Berlin prosecutors.

The DFB said they were satisfied after reading the report that the 25-year-old Hoyzer had fixed four games and had failed in two more attempts to manipulate results to favour betting on the games.

On one other occasion, Hoyer had not had to intervene to achieve the desired result, the DFB said.

One of Hoyzer's successful "fixes" was first division Hamburg SV's 4-2 defeat by regional league side SC Paderborn in the first round of the German Cup, the match that sparked the country's most serious match-fixing case since 1971.

The seven matches highlighted by the DFB on Thursday were all in the lower leagues or the German Cup.

The DFB did not comment on the first division match that prosecutors are also investigating as one of 10 games under suspicion.

Hoyzer has also stated to prosecutors that two more referees, Juergen Jansen and Dominik Marks, had sought to manipulate two matches each, the DFB said, adding that a third referee, Felix Zwayer, had also been implicated.

Of the four referees now connected with the case, only Jansen works in the top division of the Bundesliga, Germany's [Images] Football League.

"Naturally, the three referees will not be used until this is cleared up," the DFB's refereeing chief Volker Roth said in a statement.

"However, we work on the principle of presumption of innocence. If their innocence in this matter is established naturally they will return."

Prosecutors raided houses across the country on Wednesday as they widened their investigation into the case.

A total of 25 people are suspected of manipulating at least 10 matches to favour betting on the games.

As well as referees, the investigation now covers several individuals linked to two brothers identified by the initial 'S', whom media reports have identified as Croatian gamblers.

It also covers 14 players from second division and regional league clubs LR Ahlen, Chemnitzer FC, Energie Cottbus, Dynamo Dresden, Kickers Offenbach and SC Paderborn.

The DFB said they were working closely with a company called Betradar.com to establish an early-warning system to prevent further cases and would sign a contract with the company soon.

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