Toronto, Canada – By Julian Linden
The tournament referee ordered the inquiry after the alleged incident between 31-year-old Daniel and the spectator following his first round loss to Colombia's Alejandro Falla.
"The Tournament Referee's office is looking into the alleged incident," a Tennis Australian spokesman confirmed.
Witnesses courtside told a Reuters photographer that a scuffle had taken place when the woman approached Daniel, the world number 88, as he was walking away from the court after the match.
The woman was not injured in the alleged incident but witnesses said she had ended up on the ground. Photographs taken by Reuters showed mud on the back of her trousers.
Daniel was not available for comment because he had already left the Melbourne Park tennis complex when officials were notified about the incident.
Under the rules for players at grand slam tournaments, "the unauthorized touching of an official, opponent, spectator or other person" by competitors is strictly forbidden.
Players found guilty of violating the rules can face fines of up to $10,000, the International Tennis Federation said.
Tournament organizers had pledged to beef up security for this year's event after the past three championships were marred by ethnic violence.
In 2007, 150 Croatian and Serbian fans engaged in a wild brawl, hitting each other with bottles and flagpoles. In 2008, police used capsicum spray on a group of rowdy Greek supporters and last year, dozens of Serbian and Bosnian fans began throwing chairs and trading punches and kicks.
Eleven fans were thrown out of the tournament on Monday after carrying flares into the complex then disrupting a match while another four were ejected on Tuesday for unruly behavior.
(Editing by Miles Evans)