04/17/2013 03:54 EDT | Updated 06/17/2013 05:12 EDT

Boston Marathon Bombing: Investigation Leads, Ricin Letters... And Frayed Nerves (VIDEO, PICTURES, LIVE BLOG)

WASHINGTON - America’s frayed nerves found little by way of relief on Wednesday as news emerged of a poison-laced letter addressed to U.S. President Barack Obama while investigators endeavoured to close in on a suspect in the Boston Marathon bombings.

Federal agents arrested a man Wednesday in Tupelo, Miss., in connection with letters sent to Obama and a Republican senator from Mississippi. They have tested positive for ricin in preliminary analyses.

Earlier in the day, officials said they doubted the letters were linked to the bloody bombings that killed three people and injured nearly 180 others Monday at the famed marathon.

The suspect was identified as Paul Kevin Curtis, 45, of Corinth, Miss. Both letters carried an identical sign-off: “I am KC and I approve this message.” They were intercepted at off-site mail facilities and were undergoing additional testing.

The Mississippi Clarion-Ledger reported late Wednesday that Curtis was a celebrity impersonator, with Elvis Presley, Prince, Roy Orbison Buddy Holly and Kid Rock in his repertoire. A YouTube channel under the name of Kevin Curtis has dozens of videos of him performing as different famous musicians. Curtis also lamented the lack of prayer in schools in a recent Facebook post on the Boston bombings.

Multiple online posts on various websites under the name Kevin Curtis refer to a conspiracy he claimed to uncover when working at a hospital from 1998 to 2000.

The author wrote the conspiracy that began when he “discovered a refrigerator full of dismembered body parts & organs wrapped in plastic in the morgue of the largest non-metropolitan healthcare organization in the United States of America.”

The arrest came as Americans were anxious for a break in the bombing investigation. Information was being leaked to various media outlets at a fast and furious pace in an operation involving hundreds of law enforcement officials from an array of federal, state and local agencies.

At one point mid-afternoon, The Associated Press cited an anonymous law enforcement official as saying investigators had a suspect in their sights and an arrest was imminent. Other officials immediately shot down that report.

CNN went further, saying an arrest had been made. Several news outlets said investigators had identified a suspect from a surveillance video provided to them by a Lord and Taylor store located between the sites of the two explosions that rocked Boston two days ago.

CBS News, meantime, reported that the bomber was on the phone when he dropped off a second backpack containing a bomb near the finish line. Citing unnamed investigators, the network reported cellphone records resulted in the suspect’s identification.

But NBC reported police had a face, but not a name, of someone dropping off a black bag near the bomb sites who was captured on the Lord and Taylor video. The network was lauded by media watchdogs as being one of the few major news outlets that managed not to get anything wrong on Wednesday.

The FBI, and the U.S. attorney’s office in Boston, were reportedly rattled by the flood of media leaks. The FBI released a statement disputing some of the stories, but didn’t specifically say which ones were wrong except those suggesting an arrest had been made.

“Over the past day and a half, there have been a number of press reports based on information from unofficial sources that has been inaccurate,” the FBI said in a statement.

“Since these stories often have unintended consequences, we ask the media, particularly at this early stage of the investigation, to exercise caution and attempt to verify information through appropriate official channels before reporting.”

The official who spoke to the AP, however, stood by the information even after the FBI statement. An FBI news briefing was planned for later Wednesday, but was postponed by hours and eventually cancelled.

It was all sickly familiar to the tense, nerve-wracking atmosphere in the United States in the days following the terrorist attacks of Sept. 11, 2001, when traumatized Americans grappled with the aftermath of the worst such attack on U.S. soil.

At the same time, Capitol Hill offices found themselves on the receiving end of deliveries that contained anthrax spores. The perpetrator was later discovered to be unrelated to the 9-11 culprits.

The Boston bombings, about 10 seconds and 90 metres apart, showered bystanders with nails, ball bearings and other shards of metal that had been packed into at least one kitchen pressure cooker and detonated at the finish line.

The blasts tore the limbs off some victims and left a downtown Boston street soaked with blood. They also propelled shrapnel so far that police were collecting fragments from rooftops along the marathon’s route on Wednesday.

The lid of a pressure cooker was reportedly among the recovered rooftop debris.

A federal courthouse in Boston was evacuated Wednesday afternoon amid conflicting reports that a suspect was in custody inside. The U.S. Marshals Service said the building was cleared out due to a bomb threat, and a security sweep was under way.

In a jittery U.S. capital, meantime, authorities revealed that Obama was the second politician to be sent ricin in a letter postmarked from Memphis.

The newest letters touched off a scare in the U.S. capital. They read, in part, “to see a wrong and not expose it, is to become a silent partner to its continuance.”

Reports of suspicious packages and envelopes were also made in two Senate office buildings late Wednesday morning.

Police cleared out the first floor of one Senate building for more than an hour and questioned a man carrying a backpack with sealed envelopes. He didn’t end up being taken into custody.

_ with files from The Associated Press

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