A seven-year-old girl has died in Britain after she was blown about 150 metres on a bouncy castle, thought to have been swept away by a sudden gust of wind at an Easter fair.

Families had gathered at Harlow Town Park in Essex on Saturday for the third day of the event organised by Thurston fun fairs over the holiday weekend.

A woman's body has been found near Cabarita Wharf. Credit:Getty Images

A man and a woman, understood to be from the family-run bouncy castle firm, have been arrested by police on suspicion of manslaughter by gross negligence.

East of England Ambulance Service said crews 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.