THE FBI is investigating the leaking of an almost-finished version

of Hugh Jackman's X-Men prequel - partially produced by an Adelaide visual effects company.

While there is no suggestion Rising Sun Pictures leaked the film, the BBC has reported the print has a brief caption at its start with the company's name.

The working print of X-Men Origins: Wolverine is dated March 2, 2009. The film is due for global cinematic release on April 29.

It is not known whether the FBI will question Rising Sun Pictures, with the company due to make a statement later today.

Hundreds of thousands of people have already downloaded

the high quality copy of the Hugh Jackman film from several popular file sharing and streaming sites.

The version of the movie is an incomplete working print with green screens and wires attached to actors still visible.

A leak of this kind is highly unusual as pre-release security has been significantly tightened in recent years.

Access to copies of entire films is severely restricted, with effects workers given just sections to work on.

There are also measures in place to stop film being copied on to discs.

20th Century Fox said it was working to track down the source of the leak.

"We forensically mark our content so we can identify sources that make it available or download it," it said.

"The source of the initial leak and any subsequent postings will be prosecuted to the fullest extent of the law.

"The courts have handed down significant criminal sentences for such acts.

"The FBI and Motion Pictures Association of America are also actively investigating the crime.

X-Men Origins: Wolverine is directed by Gavin Hood and tells the story of how Wolverine came to be

and follows his quest for revenge after his girlfriend is murdered. It also stars Ryan Reynolds and Live Schreiber.

A press launch for the film will be held on Cockatoo Island in Sydney next Wednesday and the film will be released on April 29.