About 650 people were evacuated from the building of the Sofia Opera and Ballet on the evening of March 18 because of a strong smell, described by people at the scene as “suffocating”.
The evacuation took place at 7.20pm, during a performance.
A firefighter in the audience called the fire department. Two fire engines, ambulances and police cars were sent to the scene.
No one was injured.
An Interior Ministry statement issued about an hour after the evacuation said that the source of the smell was being investigated.
Sofia Opera and Ballet said that the interrupted performance, Prince Igor, would be repeated and tickets for the March 18 performance would be valid for the repeat.
A week earlier, Sofia shopping centre Halite was evacuated because of a strong smell, which an official statement later said was traced to cleaning fluids in the ablution block.