Italian actor Raphael Schumacher has been declared clinically dead after he was choked in a stage hanging scene that went wrong.

The 27-year-old’s family authorised the donation of his organs, and the doctors have started the procedure, a spokesperson at Cisanello Hospital in Pisa told CNN on Friday.

Police have launched an investigation into the incident and say they are trying to establish whether proper safety procedures were in place.

According to Italian news agency ANSA, four people are under investigation for manslaughter in the actor's death.

Schumacher was performing in an experimental theater production in the courtyard of Pisa’s Teatro Lux when a member of the audience noticed that the rope around his neck was too tight.

The actor’s head was covered at the time, but the spectator – a female medical graduate – saw him trembling and realised something was wrong. She ran to him, loosened the noose, and with the help of another spectator, lowered him to the ground. He was taken to hospital shortly after.

•Photo shows actor Raphael Schumacher who mistakenly hanged himself during a stage performance.