Hampshire Police say it is not yet clear when five-year-old Ashya King might return to the UK from Spain, where he was found by police this evening.
The youngster, who was being treated for a brain tumour at a hospital in Southampton, is now receiving care in a Spanish hospital.
Assistant Chief Constable Chris Shead told reporters: "It's too soon to say when Ashya will come home, quite clearly that will depend on his medical conditoin, that really is a matter for the doctors, rest assured nobody is going to do anything that will endanger his medical condition."
The head of the police force which applied for a European Arrest warrant against the parents of Ashya King has now urged their release.
A British mother whose son's life was saved by proton therapy has told ITV that she defied NHS doctors' advice to pursue the treatment.
The parents of Ashya King said they took him out of a hospital to seek proton beam treatment which is not available under the NHS.