FBI agents and bomb squads in Minnesota are hunting for explosives — or evidence of a hoax — at a high school and two other locations where suspicious packages were planted early Wednesday.

An official told FOX News that the devices found near the school, a post office and a public utility center about 6:30 a.m. "look like" bombs. But authorities in Princeton, Minn., located about 50 miles north of Minneapolis, were trying to determine Wednesday whether they were real or part of an elaborate ruse.

FBI agents were on-scene at the three locations, a law enforcement official told FOX.

The source said he was not aware of any threats that had been called in or made by whoever planted the packages.

Traffic in the area was blocked and diverted. Princeton High School and elementary school students were evacuated, and later all students from the district were sent home.

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FOX News' Mike Levine contributed to this report.