Investigators reveal information about collapse at the Apollo Theatre

Investigators are giving details about ceiling collapse at London’s Apollo Theatre.

Investigators say that collapse had to do with the plaster of Paris ties. Westminster Council said the "principal cause of the collapse was the deterioration of the hessian and plaster of Paris ties that were used to bind the timber frames supporting the suspended ceiling,” according to the Associated Press.

The ceiling collapsed while the show, The Curious Incident of The Dog in the Night-time was onstage. on Dec. 19.

Over 700 people exited the theater and upset people ran from the building. Seven people were hurt. The Apollo Theatre was built in 1901.

The venue will reopen on Wednesday with the show, Let the Right One In. The production is by the National Theatre of Scotland. This represents a return to “normal business” for Nimax Theatres, the Apollo’s owners, according to The Guardian. Some changes have been made to the theater space. A protective deck was installed under the ceiling.

The Westminster Council is sending advice to several London theaters and to English Heritage.