Sean McMinn

As the U.S. Postal Service's law enforcement arm investigates hand-made potential explosives sent to prominent Democrats and other critics of the president across the country, they have begun a process that's become a rarer one for the agency.

The U.S. Postal Inspection Service opened 19 cases related to suspicious items or substances in Fiscal Year 2017, the most recent year for which data is available.

That number is a steep drop from four years prior, when postal inspectors initiated more than 200 cases.

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