Australia's 4x100 metres freestyle relay squad confessed to taking the sedative Stilnox as part of a "bonding session" at a pre-Olympic camp in Manchester.

The AOC says the 58-year-old Walker, who is stationed at Fifth Floor St James' Hall Chambers, will immediately begin investigating the drug incident and other reported misbehaviour.

The six members of the squad - James Magnussen, Eamon Sullivan, James Roberts, Matt Targett, Tommaso D'Orsogna and Cameron McEvoy - admitted in a press conference last month to using the drug and apologised for their conduct in their hotel following a team bonding exercise.

The incident had prompted a complaint from 4x200m freestyle silver medallist Jade Neilsen, who claims she and a female team-mate were subjected to "inappropriate behaviour" by members of the relay squad, namely Magnussen, Roberts and McEvoy.

Neilsen alleged that the trio disturbed her and a team-mate with late night phone calls, door knocking and general disruptive behaviour.

The investigation is separate to Swimming Australia's Integrity Panel, chaired by former Australian Rugby Union chairman Peter McGrath

"As stated previously the AOC fully expects the athletes to give their total cooperation to Mr Walker's investigation," the AOC said in a statement.

Walker represented the AOC in its case against Nick D'Arcy in 2008 when the swimmer was banned from competing in the Beijing Olympic Games for assaulting teammate Simon Cowley.