The investigation began in February, but Federal officials aren't saying what tipped them off.

Thursday, the FBI arrested 41-year-old Melvin Thomas Neifert at his home in Selah.  The charge facing the man is Receipt of an Explosive by way of Interstate Commerce with intent to Intimidate.

The Feds raided his home in May, and reportedly found bomb making materials, consisting of potassium nitrate and other chemicals used in making an incindiary explosive device.

The FBI and other federal officials say the charges are only allegations, he is due in court August 26th. Potassium nitrate is one of the key elements in dynamite and explosives.

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