A huge search for missing 3-year-old Mikaeel Kular ended yesterday with the discovery of a boy's body 48km from his Edinburgh home.
Police investigating the disappearance have detained a person, reported by some Scottish media as his mother.
The body was found in Fife, north of Edinburgh across the Firth of Forth, shortly before midnight on Friday, local time, police said.
Mikaeel went missing from his home in Drylaw, northwest Edinburgh on Wednesday.
Assistant Chief Constable Malcolm Graham said Mikaeel's family had been informed and the investigation was continuing.
He also thanked rescue teams and the public for their "fantastic response" in helping to search.
More than 200 volunteers from the community had joined the emergency services to look for Mikaeel.
Forensic experts were to examine the body yesterday.
Police had earlier warned that Mikaeel could be missing following a "criminal act" and they had "grave concern" for his welfare.
His mother, Rosdeep Kular, told police he was missing when she went to wake him at 7.15am on Thursday. His jacket and shoes were also gone.
Police backed by a helicopter, dog teams and dozens of volunteers combed the streets of Drylaw while coastguard and lifeboat crews scoured the shoreline 800m away.
Worried police issued a UK-wide alert as overnight temperatures dropped to near-freezing.
Beauty therapist Kular is also the mother of four other children.