The investigation into poisoned letters mailed to President Barack 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 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 martial arts studio once operated by Dutschke, who hasn't been arrested or charged. 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.

Wednesday evening, hazmat teams packed up and left Dutschke's business. He was at the scene at times during the day. Daniel McMullen, FBI special agent in charge in Mississippi, declined to speak with reporters afterward.

Dutschke's attorney, Lori Nail Basham, said he is "cooperating fully" with investigators and that no arrest warrant had been issued.

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

Federal authorities have not said what led them to drop the charges against Curtis, and his lawyers say they're not sure what new evidence the FBI has found.

Both men say they have met Wicker, and they each have a connection to Holland, who received one of the ricin letters.

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, 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 crudely made form of the poison, which is derived from castor beans.

Sadie Holland has declined to comment on the case.

She 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.

Brandon Presley, Mississippi's northern district public service commissioner and a distant cousin of Elvis Presley, attended the 2007 political rally. He told The Associated Press on Wednesday that he remembers Dutschke giving a "militant" speech with personal and professional attacks against Steve Holland.

Presley, also a Democrat, said he was doing his own campaigning, though, and doesn't recall details of the speech _ just the tone of it, and the crowd's reaction.

"I just remember everybody's jaw dropping," Presley said.

Dutschke, who ran as a Republican, said his speech included sharp criticism of Steve Holland's record in public office.

Steve Holland said earlier this week that his mother made Dutschke get down on his knees at the 2007 rally and apologize. On Wednesday, he said he was mistaken about her telling Dutschke to kneel.

"She just got up and said `Sir, you will apologize," Steve Holland said.

Dutschke said Steve Holland exaggerated the incident. Presley said he remembers Sadie Holland chastising Dutschke.

Presley said of Sadie Holland: "I don't believe the woman has an enemy in the world.... I don't know anybody who doesn't love Ms. Sadie Holland, except whoever this fool is who sent the letter. Whoever it is, they ought to be ashamed of themselves, picking on Ms. Sadie."

Dutschke told AP on Tuesday that he has no problem with Sadie Holland. "Everybody loves Sadie, including me," he said.

After being released from jail Tuesday, Curtis described a long feud between himself and Dutschke, but said he's not sure exactly what started it.

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, a former martial arts instructor, 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. He is not a Mensa member. That certificate 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. He knew Dutschke also claimed to be a member of the organization for people with high IQs. 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 to meet at one point to face off in person, but Dutschke didn't show up.

"The last email I got from him, was, `Come back tomorrow at 7 and the results of you being splattered all over the pavement will be public for the world to see what a blank, blank, blank you are.' And then at that point, I knew I was dealing with a coward," Curtis said.

The voicemail for Curtis' lawyer, Christi McCoy, was full on Wednesday and she did not immediately respond to a text message. A phone number Kevin Curtis provided to The Associated Press was not working and his brother's number has been changed.

The previous day, Hal Neilson, an attorney for Curtis, said the defense gave authorities a list of people who may have had a reason to hurt Curtis, and that Dutschke's name came up.

Dutschke, who spoke with The Associated Press by telephone several times during the search Tuesday, said his house was also searched last week. He said he and his wife had gone to a friend's Wednesday because they didn't feel safe at their home.

"They ripped everything out of the house," he said Wednesday morning, adding: "I haven't slept at all."

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Wagster Pettus contributed from Jackson, Mississippi, and Associated Press writers Jeff Amy and Jay Reeves contributed from Tupelo, Mississippi.