Hollywood actor George Clooney's girlfriend Elisabetta Canalis is under investigation after a witness said she saw her snorting cocaine at a Milan nightclub in 2007.

Two years ago, authorities began investigating two Milan nightclubs that were allegedly running an escort-and-prostitution ring fuelled by alcohol and cocaine. The clubs, Hollywood and The Club, were regularly frequented by celebrities.

According to 26-year-old model-turned-prostitute Karima Menad, Elisabetta took the drug twice while partying at The Club, reports usmagazine.com.

'I remember taking cocaine with Elisabetta Canalis and two others. We were in The Club and it was December 2007. We had been at a party of some famous, rich celebrity whose name I cannot remember. I don't remember who brought the drugs but we all took it,' Menad told prosecutors in 2008.

This was revealed in documents obtained by Italian newspaper Corriere della Sera.