The International Tennis Federation has announced that two tennis umpires were banned, one for life, last year for breaches of the sport's code of conduct for officials.
Four other umpires are under investigation by the Tennis Integrity Unit, the London-based world ruling body for the sport said in a statement.
In January, tennis was rocked by a report by the BBC and online BuzzFeed News that said 16 players who have been ranked in the top 50 had been repeatedly flagged to the TIU over suspicions they had thrown matches in the past decade.
Tennis authorities rejected allegations that evidence of match-fixing had been suppressed or had not been properly investigated.
Kazakhstan's Kirill Parfenov was banned for life last February for contacting another official on Facebook in an attempt to manipulate the scoring of matches.
Croatian Denis Pitner was suspended in August for 12 months after sending information about a player to a coach during a tournament and regularly logging on to a betting account from which bets were placed on tennis matches.
Explaining why the suspensions had not been disclosed earlier, the ITF said that previously its Code of Conduct did not require officials sanctioned to be named.