(L-R) Cameron McEvoy, James Magnussen, Eamon Sullivan, Matthew Targett, James Roberts and Tommaso D'Orsogna. Magnussen and his team mates from the relay squad have admitted using a sedative banned by their national Olympic committee.

Sydney – Former world swimming champions James Magnussen and Eamon Sullivan, and their 4x100-metre relay teammates, face possible sanction from the Australian Olympic Committee after admitting taking the sleeping medication Stilnox during a “bonding session” ahead of last year's London Games.

Magnussen, Sullivan, Tommaso D'Orsogna, Cameron McEvoy, James Roberts and Matthew Targett fronted a media conference Friday with Swimming Australia president Barclay Nettlefold, and released a joint statement admitting they took Stilnox and engaged in disruptive behavior including making prank calls during the Australian team's pre-games camp in Manchester.

Roberts later said he did not Stilnox.

The medication is not banned but the AOC prohibited Australian athletes from using it ahead of the London Olympics after former swimmer Grant Hackett revealed he became dependent on sleeping pills during his career. – Sapa-AP