The Grand Slam committee administrator has opened an investigation to determine whether Williams' behaviour should be considered a "major offence".

BBC: Williams apologises after tirade

According to the Grand Slam Rule Book, unsportsmanlike conduct when referred to the Grand Slam committee can be treated as "aggravated behaviour", which "is flagrant and particularly injurious to the success of a Grand Slam, or is singularly egregious".

BBC: Williams apologises after tirade

The punishments handed down by the International Tennis Federation's Grand Slam committee could result in a U.S. Open suspension if Williams commits another major violation in any Grand Slam event in 2010 or 2011.

CNN: Serena handed suspended ban and fine