According to police the boy and some friends entered a gravel facility despite posted warning signs. The group climbed up a 2,000-cubic-metre pile of wet and heavy sand, but it suddenly shifted, burying the boy.
Rescue efforts by a plant worker and the fire department were unsuccessful. The massive pile of sand had to be moved because rescue workers were also in danger of being consumed by shifting sand, which was eventually cleared away with a wheel loader.
The boy wasn't removed from the sand for some two hours and investigators believe he suffocated, as rescuers struggled with the dangerous situation.
The boys had been grilling and swimming near the gravel plant, a police spokesperson said, adding that they had decided to enter the plant on a lark through a loose portion of the surrounding fence.