Serena Williams has been fined $US10,500 for her angry outburst at a line judge that ended a US Open semi-final.
US Open tournament referee Brian Earley says Williams has been levied the maximum possible fine for unsportsmanlike conduct, US$10,000, plus a $US500 fine for racquet abuse.
An investigation by the Grand Slam Committee will determine whether her behaviour warrants consideration as a major offence, for which additional penalties can be imposed.
US Open officials were reviewing videotapes of Williams confronting a line judge in the bizarre ending to her loss to Belgium's Kim Clijsters.
Both Williams and match umpire Louise Engzell were interviewed by Earley before they left for home on Saturday night.
Reigning champion Williams reacted to a line judge who called a foot fault by walking toward the woman, waving her racquet before her, and launching into a profanity-tinged tirade that led to an unsportsmanlike conduct violation.
Because Williams had already received a warning after smashing her racquet following the last point of the first set, the penalty point she was assessed handed Clijsters a berth in Sunday's final, which she won, beating Caroline Wozniacki of Denmark 7-5 6-3.
Williams received $US375,000 for her semi-final run at Flushing Meadows, her matches among the top drawing cards for ticket buyers and television viewers.