CNN, Reuters and other news organizations are reporting that a suspect in Monday’s deadly bombings at the Boston Marathon has been identified from video recorded at the scene.

An arrest is expected to be reported shortly.

UPDATE: Both CNN and Fox News now report that the suspect has been arrested. CNN reports:

The breakthrough came from analysis of video from a department store near the site of the second explosion. Video from a Boston television station also contributed to the progress, said the source, who declined to be more specific but called it a significant development.

A press conference in Boston scheduled earlier today has been postponed pending further developments.

UPDATE II: Jana Winter at FoxNews.com:

Investigators have arrested a suspect in the Boston Marathon bombing after  reviewing photos and video from Monday’s event, a federal source confirmed to FoxNews.com.
The suspect, who is expected to appear in federal court in Boston later  today, has not yet been named by authorities. He was seen on surveillance  footage that showed a young man carrying – and perhaps dropping – a black bag at  the second bombing scene at the finish line of Monday’s race, where two bombs  exploded, killing three and injuring 176. The camera at a Boylston Street Lord & Taylor directly across the street from one of the blasts, has given  investigators clear video of the area, according to the unnamed official.
“The camera from Lord & Taylor is the best source of video so far,” said  Dot Joyce, a spokeswoman for Boston Mayor Thomas M. Menino told the Boston  Globe. “All I know is that they are making progress.”

However, live on Fox News, Megyn Kelly has just said (as of 2:30 p.m. ET) that “senior” federal law enforcement sources deny that an arrest has been made. Viral Read staff will be liveblogging developments below.

UPDATE III: The Federal Bureau of Investigation has issued an official statement denying that a suspect has been arrested.

UPDATE IV: The FBI statement:

No Arrest Made in Bombing Investigation
FBI Boston
April 17, 2013 Special Agent Greg Comcowich
Contrary to widespread reporting, no arrest has been made in connection with the Boston Marathon attack. 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. 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 news organizations that previously claimed to have official sources telling them that an arrest had been made have not yet explained why their official sources were wrong.

UPDATE V: Liz Goodwin at Yahoo News reports:

Authorities have identified a suspect in the Boston Marathon bombings and forcefully denied news reports that an arrest had been made in the attack Wednesday afternoon.
The Associated Press and the Boston Globe reported a suspect had been arrested and was en route to the Moakley Federal Courthouse in South Boston. CNN also reported that a suspect was in custody, before backtracking from its earlier report and saying no suspect had been nabbed. The Boston Police Department and the US Attorney’s office in Boston denied those reports on Wednesday afternoon, saying no arrest had been made.
The FBI issued a sternly worded rebuke to the press for reporting that a suspect was in custody.

A press conference previously scheduled for 5 p.m. ET in Boston has been indefinitely postponed. Meanwhile, Internet users believe they may have identified at least one of the suspected bombers.