OXFORD, Miss. – The investigation into poisoned letters mailed to President Obama and others has shifted from an Elvis impersonator to his longtime foe, and authorities must now figure out if an online feud between the two men might have escalated into something more sinister.

Paul Kevin Curtis, 45, was released from a north Mississippi jail on Tuesday and charges against him were dropped, nearly a week after authorities charged him with sending ricin-laced letters to the president, Republican U.S. Sen. Roger Wicker of Mississippi and an 80-year-old Lee County, Miss., Justice Court judge, Sadie Holland.

Before Curtis left jail, authorities had already descended on the home of 41-year-old Everett Dutschke in Tupelo, a northeast Mississippi town best known as the birthplace of the King himself. On Wednesday, they searched the site of a Tupelo martial arts studio once operated by Dutschke, who hasn’t been arrested or charged.

Curtis, who performs as Elvis and other celebrities, describes a bizarre, yearslong feud between the two, but Dutschke insists he had nothing to do with the letters. They contained language identical to that found on Curtis’ Facebook page and other websites, making him an early suspect.

On Wednesday, dozens of investigators were searching at a small retail space where neighboring business owners said Dutschke used to operate a martial arts studio.

Investigators in gas masks, gloves and plastic suits emerged from the business carrying buckets full of items covered in large plastic bags. Once outside, others started spraying their protective suits with some sort of mist.

Dutschke was seen outside the studio observing the search Wednesday. His attorney, Lori Nail Basham, said Dutschke is “cooperating fully” with investigators and that as of Wednesday afternoon no arrest warrant had been issued.

Both men say they have met Wicker, and they each have a connection to Holland.

Authorities say the letters were mailed April 8, but the one sent to Holland was the only one to make it into the hands of an intended target. Her son, Democratic state Rep. Steve Holland of Plantersville, said his mother did a “smell test” of the envelope and a substance in it irritated her nose. The judge was not sickened by what authorities say was a crude form of the poison, which is derived from castor beans.

Sadie Holland was presiding judge in a case in which Curtis was accused of assaulting a Tupelo attorney in 2003. Holland sentenced Curtis to six months in the county jail. He served only part of the sentence, according to his brother.

Running as a Republican, Dutschke lost a lopsided election to Steve Holland in 2007, and observers say the judge publicly chastised Dutschke at a political rally that year.

After being released from jail Tuesday, Curtis described a long feud between himself and Dutschke.

The two worked together at Curtis’ brother’s insurance office years ago, Curtis said.

Curtis said Dutschke told him he owned a newspaper and showed interest in publishing his book called “Missing Pieces,” about what Curtis considers an underground market to sell body parts.

But Dutschke decided not to publish the material, Curtis said, and later began stalking him on the Internet.

For his part, Dutschke said he didn’t even know Curtis that well.

“He almost had my sympathy until I found out that he was trying to blame somebody else,” Dutschke said Monday. “I’ve known he was disturbed for a long time. Last time we had any contact with each other was at some point in 2010 when I threatened to sue him for fraud for posting a Mensa certificate that is a lie.”

Curtis acknowledges posting a fake Mensa certificate on Facebook, but says it was an online trap set up for Dutschke because he believed Dutschke was stalking him online. Dutschke had a Mensa email address during his 2007 legislative campaign.

Dutschke started a campaign to prove him a liar, Curtis said, and allegedly harassed him through emails and social networking.

Curtis said the two agreed at one point to face off in person, but Dutschke didn’t show up.