Image caption Everett Dutschke has links to Paul Curtis, against whom charges were dropped this week

A man has been arrested in Mississippi and charged in connection with the sending of letters containing ricin to President Obama, a senator and a judge.

Everett Dutschke was detained at home in Tupelo on Saturday and handed over to US Marshals, police said.

Mr Dutschke has been charged with possessing a biological agent with intent to use as a weapon.

He has links to a man against whom charges were filed and later dropped, as well as the senator and judge.

Ricin is a naturally occurring protein, found in the castor oil plant, which is highly toxic. It is 6,000 times more poisonous than cyanide.

List of names

Tupelo Police Chief Tony Carleton said Mr Dutschke was taken into custody without incident at 01:00 (06:00 GMT) on Saturday. His home had been under surveillance since Friday afternoon.

A law enforcement official told WTVA that the 41-year-old was being held at the Lafayette County Detention Center.

Ricin Can be fatal when inhaled, ingested or - most dangerously - injected

One to three castor beans chewed by a child, or just eight seeds chewed by an adult, can be fatal

The toxin is part of the waste produced when castor oil is made Q&A: What is ricin?

The US Attorney's Office in the Northern District of Mississippi said in a press release that Mr Dutschke had been charged with developing, producing and possessing "a biological agent, toxin and delivery system for use as a weapon, to wit: ricin".

If convicted of the federal charge, he faces a maximum life term in jail and a $250,000 fine.

The office said Mr Dutschke was expected to appear in a district court in Mississippi on Monday.

Agents from the FBI and the US Capitol Police, as well as members of an anti-terrorist response team from the Mississippi National Guard, had searched Mr Dutschke's home on Tuesday and Wednesday, as well as the premises of a former martial arts studio he ran in Tupelo.

Attention turned to Mr Dutschke after charges were dropped on Tuesday against Paul Kevin Curtis, a local Elvis impersonator.

A search of Mr Curtis' home in nearby Corinth revealed no evidence to suggest he had sent the ricin-laced letters to President Obama, Senator Roger Wicker and Mississippi Judge Sadie Holland, officials said.

Image caption Agents searched the premises of a former martial arts studio Mr Dutschke ran in Tupelo

Hal Neilson, a lawyer for Mr Curtis, said Mr Dutschke's name had been submitted on a list of people who might have had a reason to hurt his client.

Mr Curtis said he had worked with Mr Dutschke several years ago, and that they had discussed publishing a book called Missing Pieces, about an alleged conspiracy to sell body parts on the black market. Mr Dutschke decided not to publish the material, Mr Curtis added.

But Mr Dutschke told the Associated Press that he did not know Mr Curtis well, and that the last time they had contact was in 2010.

Judge Holland's family is reported to have confronted Mr Dutschke at a political rally in the town of Verona in 2007, when he ran as a Republican against her son, Steve Holland, a Democratic state representative. Mr Holland said Mr Dutschke had made a derogatory speech about the Holland family, and that his mother had forced him to apologise.

Mr Dutschke said Steve Holland had exaggerated the incident, telling AP: "Everybody loves Sadie, including me."

He is also reported to know Senator Wicker.