A "lengthy" police investigation is under way to examine how a bouncy castle lifted off the ground and blew 150 metres away at an Easter fair, killing the seven-year-old girl playing inside.
Families had gathered at Harlow Town Park in Essex on Saturday for the third day of an event organised by Thurston fun fairs over the holiday weekend.
A man, 27, and a 24-year-old woman, both from Cambridgeshire and understood to have been working for the family-run bouncy castle firm at the fair, have been arrested by police on suspicion of manslaughter by gross negligence.
Emergency services were called to Harlow Town Park shortly after 4pm to reports that a girl had been seriously injured when the bouncy castle she was on blew "some distance" away.
She was treated by ambulance crews and taken to Princess Alexandra Hospital, where she later died.
A representative for the organisers said a sudden gust of wind blew the dome-shaped inflatable over a number of trailers and caravans on the site as horrified families looked on. Police said weather conditions on the day will be a factor in their investigations.
Detective Inspector Daniel Stoten said: "The weather will certainly make up part of this investigation - whether the weather was a factor and whether or not it was appropriate for the ride to be running.
"It will be a complex and thorough investigation - I do not anticipate this to be a quick inquiry, it will be a lengthy investigation.
"We will be speaking to scientists in relation to the weight of the ride, the type of weather, the ground underfoot, the moisture content and how the ride was tethered."
Ray Smith, from the Showmen's Guild of Great Britain, said: "It was a sudden gust. Had it been a consistent wind they would have closed down all the inflatables."
Asked about how the inflatables are set up he said: "I know the family and I am very confident they had staked it out properly. Obviously there is a full investigation to be held into how this could have happened and to make sure it can never ever happen again."
The fair is closed but people visited the scene on Sunday to pay their respects to the little girl, who was from Norwich.
Among the tributes at the park's entrance is an Easter basket while another card on a bunch of flowers reads: "God has taken a beautiful girl for his angel. RIP Princess."
Detectives from the Kent and Essex serious crime directorate, which is leading the investigation, have appealed for anyone with video footage of what happened to contact them.
Councillor Jon Clempner, leader of Harlow Council, said: "Harlow is a town in shock following this tragic incident yesterday. I can't imagine the heartache of the parents and family of the little girl who has died, and my thoughts are with them." He said the council will work with all those involved, including the Great Parndon Community Association who organised the fair, in the investigations to find out what happened.
Last year a bouncy castle collapsed while children were playing on it during a funfair in the same park. It was reported at the time that three children had to be treated by paramedics when the inflatable castle collapsed on them.
Conservative MP for Harlow Robert Halfon said locals have raised concerns at another tragic incident involving a bouncy castle in the space of a year.
He said: "In the past few hours a number of residents have contacted me asking how this could happen and what is being done.
"I will be asking the relevant authorities to start an urgent inquiry as to how this tragedy happened, and to find out who is responsible, especially given events last year, and to consider whether bouncy castles such as this should be banned from Harlow Town fairs, until we can be sure that they are completely safe, so such a horrific tragedy never happens again."