Milan, November 30 - Four former mayors of Milan, Carlo Tognoli, Paolo Pillitteri, Giampiero Borghini and Marco Formentini, were on Wednesday cleared by a preliminary hearings judge in a case concerning allegations some workers died or got ill due to asbestos at the La Scala opera house before it was cleared of the material. The judge indicted five others, including former La Scala superintendent Carlo Fontana, who served from 1990-2005. The trial starts on February 9. The ex mayors were placed under investigation in their role as chairman of La Scala, which prosecutors argued gave them responsibility for environmental oversight. Besides Fontana, the defendants in the trial are ex technical director Franco Malgrande, former head of the technical department Franco Filighera, former director of general affairs Maria Rosaria Samoggia and ex health and safety consultant Giovanni Traina. They are to be tried for manslaughter and grievous bodily harm in connection with alleged asbestos-related cases starting in 1986, including singer Luciana Patelli. The world-renowned theatre was inaugurated in August 1778 and underwent a major renovation in 2002-2004.