The US Open has fined Serena Williams $USA10,000 ($NZ14,340) for her tirade directed at a line judge at the end of a semifinal loss to Kim Clijsters.
It's the maximum on-site fine a Grand Slam tennis tournament can issue for unsportsmanlike conduct.
The US Open said on Sunday the Grand Slam Committee Administrator has opened an investigation to determine whether Williams' behaviour should be considered a "major offence," which can lead to additional penalties.
Williams also is being docked $US500 for racket abuse in what became a 6-4 7-5 loss Saturday night.
Williams earned $US350,00 in prize money for reaching the singles semifinals. She also is scheduled to play in the women's doubles final Monday with her sister Venus.
