The boy, named locally as Scott Chiriseri, was found by an ambulance crew called to a flat in Alva, Clackmannanshire, yesterday morning after a member of the public dialled 999.
The boy, who is understood to have suffered a stab wound, was pronounced dead at the scene and residents of the Scottish town have today left tributes.
His mother, believed to be Zimbabwean Farai Chirashi, was being questioned by detectives last night.
Neither the boy’s father, named locally as Tichakunda Chiriseri, or his older sister Natasha, are thought to have been at home at the time of the incident.
Members of the emergency services who attended the scene are believed to have been offered counseling, according to the Daily Record.
One of the medics told the paper the boy had suffered a 'sickening and violent death'.
Local streets were cordoned off, and forensic officers were seen searching the grass outside the flat, apparently looking for the weapon involved.
Chief Inspector Stephen Sneddon said: ‘Emergency services in the Forth Valley responded to an address in Carnaughton Place, Alva, around 8.50am today in response to a call about the welfare of a five-year-old boy.
'On arrival, police officers found the child with a significant injury to his body. He was later pronounced dead at the scene by the Scottish Ambulance Service.
‘Inquiries into the full circumstances surrounding this incident are ongoing and a woman is currently detained in connection with the investigation.
‘We are not currently looking for anyone else and I want to reassure the local community that there is no risk to them.