Dozens of makeshift shields, homemade spike strips and weapons were found inside of tents Tuesday morning at Cal Anderson Park.
The Seattle Parks Department was clearing the park to repair damages done to a field house and clean up trash.
Police said workers who were cleaning out a tent in the area found what they believed were weapons.
Police obtained a search warrant to search the tent and recovered a machete, hatchet, spike strips, unexploded mortar and several makeshift shields.
No arrests were made.
The investigation remains ongoing.