TUPELO, Miss. -- Ricin was found in the former martial arts studio of the man suspected of sending poison letters to President Barack Obama and other public officials, and also was discovered on a dust mask and other items he threw in the trash, federal prosecutors said in a court document made public Tuesday.

The affidavit says an FBI surveillance team saw James Everett Dutschke remove several items from the studio in Tupelo, Miss., on April 22 and dump them in a trash bin about 100 yards down the street. The items included a dust mask that later tested positive for ricin, the affidavit said.

Traces of ricin also were found in the studio and Dutschke used the Internet to buy castor beans, from which ricin is derived, the affidavit said.

Annette Dobbs, who owns the small shopping center where the studio was located, said authorities padlocked the door to it sometime during the search. She said FBI agents haven't told her anything, including whether the building poses a health threat. Inside the studio is one large room with a smaller reception area and a concrete floor. Police tape covered the front and the small back door.

Dutschke, 41, was arrested Saturday by FBI agents at his home in Tupelo and is being held without bond pending a preliminary and detention hearing Thursday in U.S. District Court in Oxford.

The FBI searched his home, vehicles and studio last week, often while wearing hazardous materials suits. Attention turned to Dutschke after prosecutors dropped charges against an Elvis impersonator who said he had feuded with Dutschke in the past.

Dutschke said last week he didn't send the letters. His lawyer, federal public defender George Lucas, had no comment Tuesday about the information in the affidavit.

Dutschke was arrested as part of the investigation into poison-tainted letters sent to Obama, U.S. Sen. Roger Wicker and Lee County, Miss., Judge Sadie Holland.

The FBI has not yet revealed details about how lethal the ricin was. A Senate official has said the ricin was not weaponized, meaning it wasn't in a form that could easily enter the body. If inhaled, ricin can cause respiratory failure, among other symptoms. No antidote exists.

The most notable case of ricin poisoning was in 1978, when a Bulgarian dissident was lethally injected with it by an operative of that country's secret service.

Dutschke also bought 50 castor beans off eBay in November 2012 and 50 more in December 2012, the affidavit said.

The affidavit had been sealed since it was filed Friday in U.S. District Court in Oxford. It also said that on the evening of Dec. 31, 2012, someone using his "computer downloaded a publication, Standard Operating Procedure for Ricin, which describes safe handling and storage methods for ricin, and approximately two hours later, Immunochromotography Detection of Ricin in Environmental and Biological Samples, which describes a method for detecting ricin."

An expert at the National Bioforensics Analysis Center in Fort Detrick, Md., said the extraction process employed in this case appears to have been more involved than "merely grinding castor beans," the affidavit said.

A witness, who is not named in the document, told investigators Dutschke once said years ago that he knows how to make poison that could be sent to elected officials and "whoever opened these envelopes containing the poison would die."

Judge Holland dismissed a civil suit Dutschke filed in 2006 against the witness, who accused him of making sexual advances toward the witness' daughter, the affidavit said. In April, Dutschke pleaded not guilty in state court to two child molestation charges involving three girls younger than 16. He also was appealing a conviction on a different charge of indecent exposure. He said his lawyer told him not to comment on those cases.

The lawsuit isn't Dutschke's only connection to Holland. She is part of a family that has had political skirmishes with him.

Her son, Steve Holland, a Democratic state representative, said his mother encountered Dutschke at a rally in the town of Verona in 2007, when Dutschke ran as a Republican against Steve Holland.

Holland said his mother confronted Dutschke after he made a derogatory speech about the Holland family. She demanded he apologize, which Holland said he did.

Dutschke's MySpace page has several pictures with him and Wicker. Republicans in north Mississippi say Dutschke used to frequently show up at GOP events and mingle with people, usually finding a way to get a snapshot of himself with the headliner.

The first suspect accused by the FBI, Paul Kevin Curtis, 45, also had ties to Holland. Curtis was arrested on April 17 at his Corinth, Miss., home, but the charges were dropped six days later. After his arrest, Curtis said he was framed and gave investigators Dutschke's name as someone who could have sent the letters, the affidavit said.

Some of the language in the letters was similar to posts on Curtis' Facebook page and they were signed, "I am KC and I approve this message." Curtis often used a similar online sign-off.

Curtis has said he knows Dutschke and they feuded throughout the years, but he wasn't sure what caused it.

Dutschke made a brief appearance Monday in federal court, wearing an orange jumpsuit with his hands shackled.

He faces up to life in prison if convicted.

He said little during the hearing other than answering affirmatively to the judge's questions about whether he understood the charges against him. U.S. Magistrate S. Allan Alexander set his preliminary and detention hearing to take place Thursday.