The building was evacuated before the tactical unit did a controlled detonation of the so-called soda bottle bombs and a hazardous materials unit removed them, they said.
The sheriff's Bureau of Criminal Identification collected evidence.
Authorities didn't immediately say what was inside. An investigation into who was responsible was continuing, they said.
"Works bombs" have been a dangerous prank for well over a decade, despite their potential to cause severe burns or blindness when they explode.
Ordinarily, two-liter plastic bottles are filled with Drano mixed with aluminum foil.
At first glance, they look harmless. But the combination of the aluminum and the hydrogen chloride or sodium hydroxide in the fluid creates a chemical reaction that produces hydrogen gas.
When the pressure becomes great enough, they explode.
Click here to follow Daily Voice Northern Highlands and receive free news updates.