The accident occurred at 12 o'clock on Sunday in Mäntsälä, a few miles north of Helsinki. The two boys were playing on a construction site when they somehow ended up under fallen scaffolding, writes HBL.
The six-year-old was so seriously injured that he died. The other child, a five-year-old boy, has been taken to hospital with serious injuries.
The police have launched an investigation to determine the cause of death.
Corrected: An earlier version contained incorrect information about the age of the children.