A Mississippi-based martial arts teacher has been charged in connection with poison-laced letters sent to US President Barack Obama and a US senator.
James Everett Dutschke, 41, was charged with possession of the biological agent ricin, and attempting to use it as a weapon.
He was arrested at his home in Tupelo.
Ricin is a highly lethal poison made from castor beans, though the substance found on the letters is believed to be in a crude form that would prove far less lethal.
If found guilty, Dutschke faces maximum possible penalties of life imprisonment and a $250,000 (192,000 euro) fine.
His arrest comes days after US prosecutors dropped charges against another man, Kevin Curtis, who was released after a search of his home revealed no incriminating evidence.
Curtis, a professional Elvis impersonator, has had a running feud with Dutschke and suggested he may have been framed by him.