There was liaison with both schools prior to the operation.
No sports activities were taking place at the time and pupils had all gone home for the day.
Cheshire Police spokesman Daniel Hind said: “It looks like family members were clearing out a house when they found possible explosive material. They contacted us and we called the EOD (Explosive Ordnance Disposal) to carry out a controlled explosion.”
Police issued a warning on social media prior to the explosion which read: “There is going to be a controlled explosion in the Dee Banks School area of Chester. There is nothing to concern local residents.”