A man and woman in their 40s have been arrested on suspicion of gross negligence manslaughter after Ava-May Littleboy's death.
The pair, both in their 40s and from the Great Yarmouth area, are being held on suspicion of gross negligence manslaughter following the incident on Sunday 1 July.
The little girl was the only person on the attraction when eyewitnesses said they heard a "loud bang" and it "apparently burst".
Sarah Allard, who was on the beach, said Ava-May was thrown 20ft into the air. A lifeguard carried out CPR for 15 minutes before paramedics arrived, she said.
Two inflatables had been set up on the beach on what was a particularly busy day, with weekend temperatures of more than 21C.
The East of England Ambulance Service said it received more than a dozen calls about the fall.
Ava-May's family said after her death: "She was not your ordinary little girl, as anyone she met she would leave a lasting impression on.
"Her infectious laugh and smile could light up even the darkest of rooms."
Havant Borough Council in Hampshire banned bouncy castles and inflatables on its land after Ava-May's death.