Five paintings by modern masters, including a work by Picasso, have been stolen from the Paris National Museum of Modern Art, Paris Mayor Bertrand Delanoe said Thursday according to dpa. The museum's management said the stolen paintings were worth about 100 million euros (123 million dollars), making it the biggest-ever heist of artwork at a French museum. According to surveillance cameras, the theft was carried out by one individual, who apparently broke into the museum through a window. Questions were raised about the apparent breakdown of the museum's alarm system. Paris City Hall said late Thursday on its website that the alarm system had been down in several rooms for at least four weeks. The company in charge of maintaining the alarm system had been waiting for replacement parts. One of the questions investigators will be focussing on is how the thief could have known about this. The missing Picasso painting is titled Le pigeon aux petits pois, a spokeswoman for the museum said. The other stolen works are La pastorale by Henri Matisse, L'olivier pres de l'Estaque by Georges Braque, La femme à l'éventail by Amedeo Modigliani, and Nature morte aux chandeliers by Fernand Leger. The Organized Crime Brigade (BRB) is handling the investigation.