LONDON (CNN) -- The ceiling of central London's historic Apollo Theatre collapsed Thursday during a performance to a nearly packed house, injuring scores of people, four of them seriously, officials said.
"We heard a creak, somebody screamed, somebody from over there said, 'Look out!' and then the ceiling kind of creased in the middle and then just collapsed," said Hannah, who said her husband had snagged one of the last pairs of tickets to the performance in the 775-seat theater.
Though she said she herself felt "slight panic," she credited those around her for keeping their calm. "It wasn't every man for himself," she said, noting that several of her fellow theatergoers checked on those around them. "Everyone was looking out for each other, and in a couple of minutes, everyone was out."
The London Fire Brigade's Kingsland Station Manager Nick Harding said about 720 people were inside when a section of the ceiling collapsed on the theatergoers, taking parts of the balconies with it.
He put the number of "walking wounded" at 81, many of whom suffered head injuries.
"It was like slow motion," said one girl, who initially thought the sound of the falling ceiling was sound effects, but soon learned otherwise. "It just kinda came down."
"You initially thought it was part of the play and then you could feel things on you," said an older woman. "The dust that came down -- you couldn't see in front of you."
Metropolitan Police said those who were seriously hurt had been taken to hospitals in central London. None of the injuries appeared life threatening, one official said.
Authorities responded to the report at about 8:15 p.m., police said in a tweet.
Within an hour, a spokesman for the fire department said everyone, including those who had been hurt, had been evacuated from the building, which was at or near its capacity, as is customary during the Christmas season.
Martin Bostock, who was with his wife and two children, said he thought the cave-in was part of the show until something very hard hit him on the head and chaos and panic erupted.
"You couldn't see across the room because of the dust, which we were all breathing in," he told CNN. "It was absolutely horrific and very terrifying. I was with my wife and two kids. Thank God, we got out."
The Apollo is located next to Piccadilly Circus in the Soho district, which is usually packed with tourists, shoppers and diners at theater time.
Within minutes, paramedics arrived carrying stretchers as police cordoned off the area.
A few minutes later, some of the paramedics emerged from the theater, their stretcher full; others helped someone limp out of the building.
Many of the injured were taken initially to the nearby theaters.
Dozens of police, fire and ambulance vehicles filled the street in front of the Apollo.
"The Curious Incident of the Dog in the Night-Time" had been playing, which the Apollo's website described as "a thrilling new stage play from the National Theatre."
Ticket prices at the four-level theater, which opened its doors in 1901, included a 1 pound ($1.64) "theatre restoration levy," the website said.
It is owned and operated by Nimax Theatres. Once the Apollo was evacuated, an engineering team set about assessing its structural integrity.
Prime Minister David Cameron, in a tweet, commended the fast work of emergency services.