The play area was cordoned off after the incidentCredit:ANTONY KELLY/ARCHANT He said: “I’d estimate 20,000 inflatables have been hired out this weekend. This is vanishingly rare. And they’re shipped off to Spain, to Argentina – this wasn’t the heat.”He speculated one of the bed ties – which secure the internal ribbing of the bed of the unit and separate one air chamber from another – might have broken leading to internal chambers opening into one another and causing the structure to rip open or explode.A joint investigation between the Health and Safety Executive (HSE), Great Yarmouth Borough Council, and Norfolk Police has been launched to establish the circumstances surrounding the incident.It comes two weeks after fairground workers William Thurston, 29, and his wife Shelby, 26, were jailed for three years after being found guilty of the manslaughter by gross negligence of a seven-year-old girl in a bouncy castle in March 2016. Ann Weaver said: “I was sat next to it behind the barrier and I just heard a big bang and I turn around and a little girl in pink flew up and back down. They did CPR on her straight away. She looked a lot younger than four-years-old.”Brandon Lewis, Conservative MP for Great Yarmouth, tweeted: “Absolutely tragic, thoughts are with family and friends, just so sad.”Bounce About advertises five minutes on the trampoline for £2, with 15 minute sessions on other inflatables available for £3 each.Online the family business advertises rentals of rodeo bulls, bouncy castles, and bumper cars from £250.Their ‘funcity’ inflatables are marketed as being “nothing like your normal bouncy castles”, the smallest measuring 12m by 5.5m.Curt Johnson, owner of Bounce About, said it was the firm’s first major accident. He was not at the scene but said: “My condolences go out to the family after this horrific accident. I don’t know the full story. I believe it was an inflatable trampoline.”He told The Mirror the inflatable exploded “because of the heat”.The Met Office’s observatory in nearby Weybridge recorded 19.2 degrees today at 11am.The owner of an East Anglia inflatables business, who asked not to be named, said Mr Johnson and his wife either supervised children on the inflatables themselves or employed a supervisor. Norfolk Police arrived at the scene within minutesCredit:ANTONY KELLY/ARCHANT He said Bounce About has been operating on Gorleston beach for more than ten seasons, with the castles and slides inflated during the summer, and switched off and stored securely over the winter.”I know the family who look after the park and I know they look after their equipment,” he said, but rubbished the suggestion the incident could be heat-related. Summer Grant died after a gust of wind lifted an improperly secured inflatable from its moorings and sent it cartwheeling 300 metres down a hill in Harlow, Essex, the trial at Chelmsford Crown Court heard. A young girl has died after being thrown from an inflatable trampoline which exploded on a beach.Eye-witnesses have described their horror at watching the little girl in a pink dress, believed to be just four years old, thrown 20 feet into the air when the inflatable exploded with a loud bang.The Bounce About play area on Gorleston beach, just south of Great Yarmouth in Norfolk, was cordoned off yesterday and a police investigation is now underway.The play area’s owner Curt Johnson, who was not at the scene, said the trampoline had exploded “because of the heat”.Norfolk police were called to the scene at 11.15am, following reports a child had been “thrown from a bouncy castle.” Ambulance crews arrived within four minutes and the child, who was in cardiac arrest, received CPR at the scene.She was taken to James Paget Hospital two miles away but died shortly afterwards. Her family has been informed.Kara Longshaw, an eyewitness, said: “Just seen the most horrific thing in my life. A bouncy castle exploded at the beach and the child on it was catapulted about 20ft into the air. Please say a prayer for the four year old being rushed to hospital after 15 minutes of CPR.” Karen Sell said: “I heard the most enormous bang and straight away turned round. I spoke to someone who described how the girl was just thrown about 20ft into the air and landed on the floor. The bouncy castle was like a trampoline so you could jump a lot higher on it than a normal one. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.