German referee Dominik Marks has been arrested in Berlin on suspicion of fraud and money-laundering.
Marks is suspected of fixing three unspecified matches
The arrest followed testimony from referee Robert Hoyzer, who admitted match-fixing charges in January.
Berlin state prosecutors alleged that Marks is suspected of rigging the results of three unspecified matches.
He is "suspected of being involved in organised criminal activity and three cases of fraud, conspiracy to commit a crime and money laundering".
Another suspect, only identified as Tomislav C - who is aged 21 - was arrested on Wednesday and is accused of belonging to a Berlin-based gambling gang and betting large amounts of money on four matches under Hoyzer's control. He denies the charges.
Prosecutors are investigating a total of 25 people - Hoyzer, Marks, two other referees and 14 players - in connection with at least 10 matches in 2004.
Hoyzer is cooperating with prosecutors after admitting fixing matches for money from a Croatian gambling gang based at a Berlin nightclub.