A school for children with additional needs is being investigated by police after footage emerged of staff using "inappropriate restraint techniques," the BBC has learned.
North Lanarkshire Council alerted police after discovering video evidence from Clydeview School in Motherwell.
The BBC understands a member of staff has been suspended over the footage.
It shows staff restraining a nine-year-old autistic boy. The investigation concerns a "small number" of pupils.
Parents of children at the school have been informed.
In a letter Derek Brown, North Lanarkshire Council's joint interim director of children and families, wrote: "We have discovered evidence of what, on the face of it, appears to be inappropriate use of pupil restraint and inappropriate restraint techniques being used."
Mr Brown told parents the evidence was "historical and not current".
But he added: "It will be for the police to investigate and determine whether a criminal offence has taken place."
It is understood that the most recent allegations date back to June 2018.
The development comes just days after Education Scotland produced a withering inspection report on the school, describing it as "weak" in two categories - Learning, Teaching and Assessment, and Raising Attainment and Achievement.
It was also graded "unsatisfactory" in the categories of Leadership of Change, and Ensuring Wellbeing, Equality and Inclusion.
The inspectors also called for a series of measures, including a review of child protection documentation and additional staff training.
Police Scotland confirmed detectives are examining the evidence.
A force spokeswoman said: "An investigation is under way after Police Scotland was made aware by the local authority of concerns about the conduct of staff at a school in North Lanarkshire.
"Inquiries, which are at an early stage, are under way."
A North Lanarkshire Council spokesman said: "Video evidence has come to light showing what appears to be inappropriate use of restraint and the deployment of inappropriate restraint techniques involving a small number of pupils at Clydeview School.
"The safety and wellbeing of children in our care is our primary concern and, on being presented with this material, we took immediate steps to launch a formal investigation.
"Given the nature of some of the video evidence, we also immediately contacted Police Scotland."
The spokesman added: "Both of these investigations are at an early stage and we will keep parents updated as they progress.
"The safety of children is paramount and we are confident that there is no risk to children attending the school."
Last year Scotland's children and young people's commissioner expressed concern about the "ungoverned" and potentially illegal use of restraint and seclusion in the country's schools.
Bruce Adamson told The Guardian: "We are deeply concerned that significant physical interventions may be taking place without any kind of policy or procedure at local authority level to ensure the lawful and rights-compliant treatment of children."