It comes two days after police arrested two men in the town of Cullompton, 280km southwest of London, close to the 24-year-old millionaire singer's family home in Devon.
Both men are due to appear at Exeter Magistrates' Court on Thursday.
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Police were said to have found a body bag, rope and a sword inside a red Fiat Punto, Britain's Telegraph paper reported.
Stone's London publicists, DWL, said the singer was aware of the arrests. They would not say whether Stone was at home when the men were arrested.
Stone said in a statement that she was "absolutely fine and getting on with life as normal".
Stone came to fame in 2003 as a small-town teenager with a big, soulful voice, showcased on her best-selling debut album The Soul Sessions and hit singles including Fell In Love With A Boy.
She won a Grammy Award in 2007 in the R&B category for her collaboration with John Legend and Van Hunt on a cover of Sly and the Family Stone's Family Affair, and is a member of rock
supergroup Super Heavy with Rolling Stone Mick Jagger, reggae scion Damian Marley and Dave Stewart of Eurythmics.
She has also taken acting roles, including that of Henry VIII's fourth wife, Anne of Cleves, in TV drama The Tudors.
With a fortune estimated last month by the Sunday Times Rich List at STG9 million ($A13.86 million), she still lives in the rural southwestern county of Devon where she was raised.
She is a friend of Prince William and was a guest at his wedding to Catherine Middleton in April.
Stone is due to start a European tour in July.
