MARSEILLE - Marseille's Velodrome stadium could be unavailable for two months because of the ongoing inquiry after a stage built for a Madonna concert collapsed earlier this month, a city official said on Tuesday. Two workers were killed when part of the roof over the stage being built for the pop singer's concert collapsed on July 16. Marseille public prosecutors have launched an inquiry into the deaths. A police source said one of the four cranes used to erect the stage slipped, causing the roof to buckle. "The experts have effectively asked for two months to finish their inquiry," Marseille deputy Mayor Maurice Di Nocera told Reuters. Marseille prosecutors declined to comment. The delay, needed for experts to analyse the scene of accident, means former European champions Olympique Marseille would not be able to play at their Velodrome stadium until September. Marseille might have to look for another stadium for their first two home games in the 2009-10 season, against Lille on August 16 and champions Girondins Bordeaux on August 30. "People have paid for their season tickets and we have 55,000 people at every game at the Velodrome," Di Nocera said. A French rugby championship match between Toulon and Racing Paris scheduled at the Velodrome on Aug. 22 might also have to be staged elsewhere.