A five-year-old boy was found with his heart ripped out in a suspected 'ritual' killing.
Police Scotland launched a murder investigation in Alva, Clackmannanshire, after finding the child following calls about his welfare.
A woman, who is believed to be the boy's mother, was held by police on Friday night. It is understood she is from Botswana, and there is another child, the boy's sister, who is safe and well.
An emergency crew member said the boy suffered a "sickening and violent death".
Police described the victim as have a "significant injury" to his body, according to the Daily Record.
Paramedics declared the boy dead at the scene and the streets around the end-of-terrace house in Carnaughton Place were cordoned off. Forensic teams searched the area outside the flat.
Chief Inspector Stephen Sneddon said: "On arrival, police officers found the child with a significant injury to his body and he was pronounced dead at the scene by the Scottish Ambulance Service.
"Inquiries into the full circumstances 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 there is no risk to them. Officers will be carrying out inquiries in the area and I would ask the public to continue to give us the full support they have shown so far, to allow us to conclude these investigations as soon as possible.
"Officers will be carrying out inquiries in the area and I would ask the public to continue to give us the full support they have shown so far, to allow us to conclude these investigations as soon as possible.
"This is a quiet area and I would emphasise that this is a very unusual incident which poses no risk to others."
A neighbour described the mother of the boy as "quiet".
Victoria Thomson said: "She moved there a wee while ago, maybe last year. They haven't been there long.
"She lived there with her two children. The other one was a wee girl. The wee boy was five but that is all I know.
"I don't think she had a partner. She was a really quiet lady. She always had her curtains shut as well."
Police Scotland said they were not looking for anyone else in connection with the incident.
Dr Hendrik Scholtz, a South African expert in ritualistic murders, explained that human sacrifice takes place when people need to obtain supernatural powers to be successful in something like business or politics.
He said: "The person is sacrificed to awaken the supernatural force required to attain that goal."