No one was injured in the fire, according to the BBC, though there may be smoke damage in parts of the building.
The program for the concert was to be Matthias Pintscher's H_rodiade-Fragmente, featuring soprano Marisol Montalvo, and Beethoven's Symphony No. 9.
Due to the tight scheduling of both the Prom concerts and the orchestra's itinerary, tonight's concert cannot be rescheduled. The Royal Albert Hall will refund ticketholders' money.
The BBC and the venue confirmed today that this evening's Prom concert with the Philadelphia Orchestra (featuring the Fifth Symphonies of Beethoven and Tchaikovsky) and late-night Prom (with Leonidas Kavakos and the Camerata Salzburg playing Mozart and Haydn) will proceed as planned.