The U.S. Open has fined Serena Williams $10,000 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 U.S. Open said 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 $500 for racket abuse in what became a 6-4, 7-5 loss on Saturday night.

Williams earned $350,000 in prize money for reaching the singles semifinals. She also is scheduled to play in the women’s doubles final on Monday with her sister Venus.

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