- Pair were caught with plans to the star's home
The pair were caught in a car near her home with weapons - thought to be swords - along with a body bag, plans to her house and rope.
Police said the two men, aged 30 and 33, were arrested in Cullompton, Devon, at about 10am yesterday.
Detectives said the men were initially arrested for possession of offensive weapons and being equipped to steal.
Officers found swords, rope and a body bag when they arrested the men near the 24-year-old star's isolated country home, the Sun reported.
The men also had detailed maps and aerial photos of her rural property, it was reported.
A Devon and Cornwall Police spokesman said: 'Police attended an address in Cullompton yesterday morning after alert residents notified officers about a suspicious-looking vehicle.
'Officers attended the area at around 10am and subsequently arrested the occupants of a red Fiat Punto.
'Major crime detectives are continuing to investigate.'
Last month the Sunday Times Rich list placed Stone, who grew up in Devon, as the fifth-wealthiest British and Irish pop star aged under 30, with a fortune of £9million.
None of the singer's representatives were available for comment this morning.
However, a source added: 'The pair were brought in on Tuesday morning and are in the cells. They are being quizzed about a plot to cause Joss Stone really serious harm.
'They have their solicitors with them but the police want to know what lies behind this.'
Joss Stone lives in Devon when she is not touring. It is not clear whether she was at home when the two men were arrested but it is known she is due to go back on tour next month.
As well as her home near Cullompton in east Devon, her mother runs a popular music venue called Mama Stones nightspot in Exeter 20 miles away.
The singer was a guest at the Royal Wedding after becoming a friend of Prince William.
Up to 20 detectives from the major crime unit are involved in the inquiry.
'A body bag, swords and maps of where she lives in mid Devon were recovered.'
Detective Inspector Steve Parker, who is leading the investigation, said: 'The two men in custody had in their possession information relating to an individual in the Cullompton area and items which lead us to suspect that they may have intended to commit a criminal offence.
'Police inquiries continue and the men remain in custody.
'We're unable to say any more at this time but I would like to thank the local residents for reporting the suspicious car.
'Our officers are currently carrying out reassurance patrols and it's important to stress that no properties have been burgled and no individuals have been harmed.'
A local farmer said he had not see Joss, 24, at the farmhouse she bought but said she had spent money renovating the buildings and buying an adjacent field.