Three children are in a critical condition after being rescued from a fire at a derelict building.
Emergency services were called to the blaze on London Road in Stockport on Tuesday evening.
The three children, whose ages have not been released, were rescued by firefighters and remain in hospital in a critical condition, Greater Manchester Police said.
Officers believe the fire may have been started deliberately and have also appealed to parents and carers to explain to children the dangers posed by playing inside disused buildings.
Detective Inspector Chris Aunins said: "We have launched an investigation in conjunction with Greater Manchester Fire and Rescue Service into how the fire started.
"We believe that it may have been started deliberately and so we are appealing for anyone with information, or anyone who may have dashcam footage, to get in touch with police to help with our inquiries.
"Now we are in the school summer holiday period, I'd like to appeal to parents and carers to explain to children the dangers of playing within disused buildings, as they pose a really serious risk with a number of potential dangers within them."
The fire service confirmed it was called to reports of a blaze at about 8.30pm and said "three children were rescued from the building by firefighters and were conveyed to hospital by paramedics".
Anyone with information can contact 0161 856 9821 or 101 quoting log number 3142 of the 26 July - or call Crimestoppers, anonymously, on 0800 555 111.