The discovery at a Tooele home about 6 p.m. Wednesday prompted officials to evacuate about 20 houses. The area was cleared at about 10 p.m.
Police say the homeowner was doing maintenance on the subfloor of his home when he found the boxes labeled "Explosives/TNT."
Tooele Community Services supervisor Bucky Whitehouse says the soap got wet and started to foam, which is a common phenomenon of aging and volatile dynamite.
The Unified Fire Authority Bomb Squad used X-ray to determine the packages weren't explosives. They later found the contents were labeled as soap.