The roof and stage of the opera house in Bonn, Germany, have been damaged after a small fire on Monday.
Repair work is expected to last until mid-September
The blaze started in the roof, where welding works were being carried out, authorities have said.
There were no reported casualties but the fire and smoke plus water from firefighters also caused considerable damage to the stage and wings.
The venue is currently in the middle of its summer break and few people were in the building.
All of the former German capital's professional and volunteer firefighters were called to the scene.
Repairs are expected to last until mid-September, which would hit the start of a Beethoven festival on 8 September.
The venue suffered another fire 20 years ago during a
performance of Serge Prokofiev's The Fiery Angel.