The suspect charged with sending letters laced with the poison ricin to President Obama and Sen. Roger WickerRoger Frederick WickerGOP senators introduce bill to prevent family separations at border Overnight Defense: States pull National Guard troops over family separation policy | Senators question pick for Afghan commander | US leaves UN Human Rights Council Senators question Afghanistan commander nominee on turning around 17-year war MORE (R-Miss.) was released from custody on bond Tuesday after authorities failed to turn up evidence of the poison in a search of his home. 

Paul Kevin Curtis was released after authorities canceled his latest hearing, which had been scheduled for today. 

There was no initial explanation for the release, but federal officials and Curtis's defense attorney plan to speak at a press conference at 5 p.m. CDT, according to The Associated Press. 

On CNN, Curtis’s attorney, Christi McCoy, said the case had not been dismissed even though Curtis was released on bond. McCoy would not go into the specifics of the bond.

"All of the conditions of the bond are under seal at this point," McCoy said.

J. Everett Dutschke told The Associated Press that the FBI had searched his home as part of the investigation into the letters. McCoy previously suggested that Dutschke could be responsible for the mailings.

Authorities failed to find any trace of the ricin poison at Curtis's home during searches after he was charged with sending the letters. 

A search of Curtis's home in Corinth, Miss., found no trace of ricin, and searches of his car and his ex-wife's home also came up empty.

"There was no apparent ricin, castor beans or any material there that could be used for the manufacturing, like a blender or something," FBI Agent Brandon Grant told The Associated Press.

Ricin is a poisonous substance made from crushed castor beans that is deadly to humans, even in tiny amounts.

U.S. Marshal Jeff Woodfin said Curtis had been released on bond.

Curtis has denied sending the letters, which were postmarked on April 8 and sent from Memphis, Tenn. The letters were signed, "I am KC and I approve this message." Curtis allegedly used that phrase in writing about conspiracies. He referred to himself as KC on his Facebook page.

Curtis's attorney has suggested someone else sent the letters.

Among the exhibits submitted for Curtis's case are a letter for the Social Security Administration and "mental papers" filed in Prentiss County, Miss., according to court records.

Letters to Obama and Wicker showed traces of the poison. The letters were intercepted before they reached the intended recipients but not before putting the Capitol on edge resulting in increased security.

White House press secretary Jay Carney said Tuesday that he didn't know whether the president had been briefed on Curtis's release, referring questions to the FBI.

Jordy Yager and Justin Sink contributed to this story. 

This story was last updated at 4:25 p.m.