Nick Harding from London Fire Brigade said the audience at the Apollo Theatre were walking around in a dazed condition after the ceiling collapsed.
The Kingsland Fire Station manager said, "People were in a lot of shock ... a lot of them had head injuries and other injuries so it was quite a confused scene."
More top news
After the Indiana polls close, ITV News asked Ted Cruz supporters if they could back Donald Trump as the Republican presidential nominee.
With his massive victory in Indiana, Donald Trump can now not be stopped from becoming the Republican nominee.
Donald Trump is predicted to win the crucial Republican Indiana primary, US media have projected.