OXFORD, Miss. - A dust mask that tested positive for ricin also contained DNA from a Mississippi man suspected of sending poison-laced letters to President Obama and others, an FBI agent testified Thursday.

The testimony came during a preliminary hearing for James Everett Dutschke, 41, who was arrested Saturday at his home in Tupelo and charged with making ricin, the same substance mailed on April 8 to Obama, U.S. Sen. Roger Wicker, and Mississippi Judge Sadie Holland.

Magistrate Judge S. Allan Alexander ruled that there was enough probable cause to send the case to a grand jury. It's not clear when one would hear evidence in this case.

Dutschke's attorney, George Lucas, waived a detention hearing, but reserved the right to ask for one later. That means Dutschke will remain behind bars for now.

FBI agent Stephen Thomason said that on April 22, agents saw Dutschke go to his former martial arts studio in Tupelo and then throw items in a trash can down the street. One of those items was a dust mask that tested positive for ricin, he said.

Thomason said the mask had DNA from two people on it.

He said Dutschke was the "major contributor." The agent did not say who else's DNA was on it.

Dutschke is second person to be charged in the case. The first suspect, Elvis impersonator Paul Kevin Curtis, 45, was arrested on April 17, 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, according to an FBI affidavit filed in federal court.

Curtis said he knows Dutschke and they feuded over the years.

During Thursday's hearing, Dutschke scribbled notes at times and shook his head in disagreement at some of the testimony.

No possible motive was discussed.

Much of Thomason's testimony was from an FBI affidavit made public earlier this week.