LONDON — Hunks of plaster and dust rained down on a packed audience when the ceiling of a London theater partially collapsed Thursday night. More than 75 people were injured — seven seriously, authorities said.The collapse at the Apollo Theatre took place around 8:15 p.m. during a performance of The Curious Incident Of The Dog In The Night-Time at the height of the Christmas holiday season. Plaster and masonry from a section of the ceiling tumbled down, bringing parts of the theater’s balconies down with it onto the audience, police said. More than 700 people were in the theater at the time, according to the London Fire Brigade. Officials said most of the injured were “walking wounded” with upper-body injuries, and that all are conscious and breathing. Police and fire officials said it was too soon to say what had caused the partial collapse of the ceiling, but that a full investigation is being carried out. Scott Daniels, a native of Fort Worth who now lives in Carrollton, said he’d managed to buy a last-minute ticket to the acclaimed production just before show time. “I was lucky to get one seat that they had left over,” he said. About 40 or 45 minutes into the show, he said, “I started hearing noises — screaming.“I thought, maybe this is part of the play,” he said. “All of a sudden, plaster starts raining down, huge hunks of plaster … The lights went out and everything filled with dust – everybody was coughing and choking.” He said he made it out with “a couple scrapes,” though he saw others with more serious lacerations. Dust-covered theatergoers, many with bandaged heads, were treated by dozens of emergency workers in the street outside the Apollo and at a nearby theater.City buses were used to get some of the injured to hospitals. Initially, London Ambulance Service said more than 80 people had been injured. But noting that the initial situation was confusing, it later adjusted that number to 76 patients, 58 of whom were taken to hospitals. The Apollo Theatre, named for the Greek and Roman god of music and the arts, was built in 1901 and has 775 seats.