Paul Kevin Curtis, charged with sending the letters, appeared in a federal courtroom today in Oxford, Miss., where he maintained his innocence.
The letters were postmarked in Memphis, almost 100 miles from Curtis' home in Corinth, Miss. It had no suspicious markings and no return address, the office of the Senate sergeant-at-arms told the New York Times.
The letters were thought to contain ricin, but had to be sent to FBI labs in Quantico, Va. for further examination, as field tests for ricin are unreliable.
Wicker had met Curtis before at a party he and his wife were holding for a young couple they knew. Curtis works as an Elvis impersonator in north Mississippi.
The Clarion-Ledger wrote that Curtis is known for his beliefs in conspiracy theory, including claims that "he is on the front lines of a hidden war machine against the mafia and a black market organs harvesting scheme," according to his Facebook page. An acquaintance described his future campaign for President of the United States as having two criteria: one million dollars for everyone, and that bars stay open until 7 a.m.
Curtis has written letters to officials before, but no previous letters were biologically threatening. Ricin can be fatal if ingested or inhaled. No one was exposed to the ricin during the handling of the letters.
If charged, Curtis could face up to 15 years in jail and $500,000 in fines.
Toddler uninjured after being knocked over by Obama family dog
Exploding whale video goes viral on Internet