An unfinished copy of U2's upcoming CD (search) disappeared while the Irish rock band was posing for the album cover in a studio outside Nice.

About 20 people who were at Tuesday's photo shoot were questioned by police, who said Thursday it was unclear whether the CD's disappearance was accidental or theft.

In a posting on U2's Web site, guitarist The Edge (search) said: "A large slice of two years' work lifted via a piece of round plastic. It doesn't seem credible but that's what's just happened to us ... and it was my CD."

According to the Web site, the band recently completed much of the new album in Dublin and have been involved in post-production work in France.

The CD is the first new studio album from U2 since 2000's "All That You Can't Leave Behind." (search) The new album is scheduled for release this fall.