The collapse occurred just after 8:15 PM GMT with some 85 patrons injured in the event, seven of them with serious injuries as a result. Three London hospitals are currently treating the wounded. Broken legs and head wounds have been reported.
Witnesses reported hearing a "strange crackling" noise prior to the "entire dome roof" of the Apollo Theatre collapsing onto patrons below. Many in the audience initially believed the noise was part of the performance.
The London Fire Bridgade stated that a portion of the theatre's domed ceiling collapse, taking with it part of the lighting rigging for the production. Kingsland Station manager Nick Harding stated, "A section of the theatre's ceiling collapsed onto the audience who were watching the show. The ceiling took parts of the balconies down with it."
Police said that all those intitially trapped in the collapse have now been freed by first responders. No fatalities have been reported and authorities are currently awaiting a full structural assessment of building.
"You could see everyone ran off the stage... it went dark," a witness told the BBC. Patrons were seen exiting the theatre covered in dust. Eight fire engines are currently on the scene, according to the London Fire Brigade.
"All the actors reacted, we saw all the actors looking up above us and pointing, looking horrified and then things started falling and smoke, and I thought it was part of the show until something hit me on the head very hard," theatregoer Martin Bowstock told the BBC.
Much of London's theatre VIP scene was at the opening of the new Andrew Lloyd Webber musical Stephen Ward at the Aldwych Theatre.
The Apollo Theatre, which opened in 1901, is located on Shaftesbury Avenue in London's West End. The theatre is owned and operated by Nimax Theatres and has 775 seats over four levels. Nimax also owns and operates London's Lyric, Garrick, Duchess and Vaudeville theatres.
A spokesman for Niamx Theatres described the ceiling collapse as a shocking and upsetting incident, and that thoughts are with audience and staff caught up in the incident. Adding that an investigation into the cause was underway.
The Curious Incident Of The Dog In The Night-time transferred to the Apollo after a sell-out run at the National Theatre's Cottesloe Theatre last year. The production won seven Olivier Awards, including Best Play.
Recent productions at the Apollo include Jez Butterworth's acclaimed drama Jerusalem, starring Mark Rylance; as well as All My Sons starring David Suchet and Zoë Wanamaker; the Donmar Warehouse transfer of Mary Stuart, which later played Broadway; Kathleen Turner in Who's Afraid of Virginia Woolf?; The Country Girl, Fool for Love, Summer and Smoke, The Glass Menagerie, Kean, Glengarry Glen Ross, The Vortex, Rain Man, Three Days of Rain, Carrie’s War and The Gruffalo.
Playbill.com will continue to update our report on the developing story.