Dressed in black and bearing a bouquet of roses, the Material Girl embraced the widow of 53-year-old Frenchman Charles Criscenzo who lost his life in the tragedy. Charles Prow, a 23-year-old British worker from Leeds was also killed when a roof collapsed.
Madonna, who made bedside visits to the eight people remaining in hospital, made a special mention of the two men who died during her stage show in Italy.
"I just wanted to take a moment to acknowledge and pay tribute to two people who lost their lives today," the tearful star told fans. "It's a great tragedy to me. I feel so devastated to be in any way associated with anyone's suffering.
"Let's all just take a moment to say a prayer for Charles Criscenzo and Charlie Prow. Our hearts go out to their family and loved ones."
Workers had been setting up the stage at the Velodrome stadium in Marseille when the partially completed roof fell in, bringing down a crane with it. About a dozen of the 50 technicians who were putting up the set were underneath the roof when it came down. The concert, which had been scheduled for Sunday, was cancelled.
Prosecutors have opened a manslaughter investigation following claims that one of the cranes being used to lift the giant roof structure was faulty.