Casey Cutler, 25, of Mesa, was arrested Saturday after a man who was hospitalized complained that Cutler may have poisoned him with ricin. Federal prosecutors say Cutler will be formally charged this week.
The hospitalized man, whose name was not released, showed no signs of exposure to ricin, but ricin was discovered in Cutler's possession when he was arrested Saturday in a public place in Mesa, police said.
Officials said he wasn't known to have any connection to terrorism, but gave no details on what or whom he might have been targeting.
"This is an isolated incident,'' said Keith Bennett, assistant special agent in charge of the FBI's Phoenix field office.
According to the Centers for Disease Control and Prevention, as little as 500 micrograms of ricin, roughly the amount that fits on the head of a pin, is enough to kill an adult. The poison can be made from waste left over from processing castor beans.