The three suspicious packages discovered in Princeton, Minn. on Wednesday did not contain any hazardous materials, the Princeton Police Department announced today.
Testing revealed that the packages contained only "inert powders."
The discovery of the devices prompted schools to close and explosives experts to comb the town of 4,500 with bomb-sniffing dogs. Officials gave the all-clear Wednesday afternoon and students returned to class Thursday morning.
Police Chief Brian Payne says each package contained some sort of bottle that was heavily wrapped with tape, and had wires running into it.
The packages were found outside the Princeton high school, behind a post office, and at the city's public utilities office.
Investigators also found five "chemical reaction devices" left on both ends of a roadway running through the city.
The devices, commonly referred to as "McGyver bombs," are plastic beverage bottles, typically filled with an explosive combination of common household liquids.
The police have not released any other information on the five devices.
Investigators have no suspects in the case, but have identified several "persons of interest."
On Thursday, the U.S. Postal Inspection Service announced a $10,000 reward for information leading to the arrest and conviction of the person who left the package behind the post office.