Melbourne:Extra security guards were added at the Australian Open after a boy was allegedly sexually assaulted in the toilets at the main stadium, officials said on Friday. Victoria state police said the boy was touched inappropriately by a man inside toilets in the Rod Laver Arena on Monday evening, and detectives from the force's Sexual Offenses and Child Abuse Unit were investigating. The boy's age and other identifying details were not released. Tennis Australia chief executive Steve Wood said organisers were cooperating fully with the investigators, who had initially asked the incident not be made public. He said extra security staff had been added to patrol the Melbourne Park venue, and all guards had been told to be "sensitive to this type of incident." "We were deeply shocked by this incident," Wood said. "The welfare of our patrons has always been a top priority and we are working extremely closely with the police to support them in every way we can in this investigation." Wood said organisers had not made the assault public previously because "our hands have been tied by the police investigation". It was the second time police have been called in to the tournament. On Monday, gangs of Croatian and Serbian youths clashed briefly in a public area of the tournament. Authorities threw about 150 people out of the venue, and no further trouble has been reported.