A mother has been arrested on suspicion of poisoning her 12-year-old son while on holiday in Devon over the Christmas period.
The boy is currently being treated in Torbay Hospital. His condition is not thought to be life-threatening.
Devon and Cornwall Police were alerted by social services staff based at the hospital.
Det Sgt Rob Kingdon said it was a "challenging and very, very sensitive, sad investigation".
He said it was too early to say how the child had been poisoned, but a criminal investigation into the administering of a noxious substance was being carried out.
"Medical staff are assisting us with regard to identifying certain drugs that have been given to the child, but it's at the very early stage of our investigation," he told BBC News.
It is hoped the boy will be well enough to speak to police later.
The family live outside the force area, but have links to Devon.
The mother has been released on police bail until 1 March.