Two giant lighted M's flank the stage of Madonna's Sticky and Sweet concert set, seen here at the Stade de France stadium near Paris in 2008. The elaborate stage design includes myriad lights, screens, moving platforms and, at one point, a vintage Rolls Royce.Two giant lighted M's flank the stage of Madonna's Sticky and Sweet concert set, seen here at the Stade de France stadium near Paris in 2008. The elaborate stage design includes myriad lights, screens, moving platforms and, at one point, a vintage Rolls Royce. (Thibault Camus/Associated Press)A French city official says an upcoming Madonna concert in Marseille has been cancelled following a stage collapse on Thursday that killed a worker and injured nine others.

Fire department officials said a roof section of the stage fell on top of several workers at the Stade Velodrome stadium on Thursday. The complex and intricate set was being built in advance of the southern French city's stop on Madonna's ongoing Sticky and Sweet tour.

The cause of the collapse remains unclear.

Maurice Di Nocera, the Marseille city councillor in charge of major events, said workers had completed about two-thirds of a roof section before it gradually fell apart onto the builders.

"Since it did not collapse right away, that allowed several people to get out, to avoid being hit," he said on France-Info radio.

Di Nocera added that the concert — slated for Sunday — has been cancelled.

Authorities said two of the nine injured workers are in serious condition (an American and a British citizen), and all victims have been taken to area hospitals for treatment. The identities of the deceased, French worker and those injured have not been released.

Madonna has been on a record-breaking world tour promoting her latest album, Hard Candy, since last year. In February, her camp announced she would extend the tour by adding a host of new dates across Europe.

With files from The Associated Press