A Mississippi martial arts instructor was charged on Saturday with attempting to use a biological weapon after a ricin-laced letter was sent to President Barack Obama earlier this month, the US Department of Justice said.

Everett Dutschke, 41, was arrested at his Tupelo home shortly after midnight by FBI agents following searches of the residence and a former business as part of the ricin letter investigation.

He was later charged with "developing ... and possessing" ricin and "attempting" to use it "as a weapon", according to a joint statement by the US attorney for the northern district of Mississippi and the head of the FBI's Mississippi office.

Ricin is a highly lethal poison made from castor beans.

If convicted, Dutschke faces maximum possible penalties of life imprisonment and a $250,000 fine.

His arrest came several days after US prosecutors dropped charges in the case on Tuesday against another Mississippi man, Kevin Curtis, who was released from jail after a search of his home revealed no incriminating evidence.

Dutschke's name first surfaced when Curtis' attorney suggested in a court hearing that her client had been framed by someone, and mentioned a running feud between Dutschke and Curtis.

Saturday's announcement did not specify if Dutschke was being charged in relation to the ricin letters, but it noted that the investigation had been conducted by several federal agencies including the US Postal Inspection Service and US Capitol Police.

Dutschke's attorney, Lori Basham, did not return calls seeking comment, but she told Reuters earlier in the week that her client denied having anything to do with the ricin letters.

Dutschke is expected to appear in US District Court in Oxford, Mississippi, on Monday.

Federal agents initially targeted Curtis, an Elvis impersonator, in their efforts to find who sent the letters laced with ricin.

Letters addressed to Obama and Senator Roger Wicker, a Mississippi Republican, were retrieved last week at off-site mail facilities before reaching their intended victims. A Mississippi state judge also received a ricin-laced letter.

Discovery of the letters fueled more national anxiety in the days after the bombing at the Boston Marathon.

The case also brought extra scrutiny for the FBI almost 12 years after a 2001 letter-borne anthrax attack that killed five people and puzzled investigators for years. The anthrax investigation came in the wake of the Sept 11, 2001, hijacked plane attacks on the United States.

Federal agents in unmarked vehicles were stationed in streets surrounding Dutschke's home on Friday afternoon and all evening.

Agents from the FBI and members of an anti-terrorist response team from the Mississippi National Guard, some wearing hazardous material suits, had searched the home on Tuesday and Wednesday, as well as the premises of a former martial arts studio Dutschke ran in the city.

Dutschke was cooperating with federal officials during the searches this week, his attorney said.

Suspicion had originally fallen on Curtis because of wording contained in all three ricin letters, which included his initials "KC".

Reuters

(China Daily 04/29/2013 page4)