UPDATE: The FBI offers its own definitive—and media shaming—statement (emphasis ours):
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.
Update 2:58 p.m.: CNN has now completely walked back their original report that an arrest has been made. (The AP and Fox News, however, appear to be sticking to their stories for the moment.) Shortly after the Boston Police Department came out with a rather definitive statement:
Despite reports to the contrary there has not been an arrest in the Marathon attack.— Boston Police Dept. (@Boston_Police) April 17, 2013
BREAKING NEWS: No arrest made in bombings, US attorney, Boston police say. bostonglobe.com/?refresh=true— The Boston Globe (@BostonGlobe) April 17, 2013
Update 2:30 p.m.: CNN continues to be out in front on this story (potentially too much so), reporting that an arrest has been made. Other outlets are less certain about exactly how far along in the process we are. While no one's sources seem to be refuting the idea that the FBI has IDed a suspect (at least his face, if not his name) and that an arrest may be on its way, it remains unclear whether that man is in custody and/or if he's been formally arrested.
BREAKING: Law enforcement official: Arrest imminent in Boston Marathon bombing, suspect to be brought to court.— The Associated Press (@AP) April 17, 2013
MORE: Suspect taken into custody in marathon bombing, expected in federal court:apne.ws/13jjJem -BW— The Associated Press (@AP) April 17, 2013
BREAKING NEWS: Globe source: An arrest is imminent in the Marathon bombings. AP reporting suspect in custody.— The Boston Globe (@BostonGlobe) April 17, 2013
LATEST: "All we can say for certain, is that all of our sources say no arrest" - NBC’s Pete Williams on Boston investigation— NBC News (@NBCNews) April 17, 2013
Original Post 1:25 p.m.: CNN's John King reports that authorities have made a "clear identificaiton" of a suspect in Monday's Boston Marathon bombing largely from video surveillance recorded at the scene by a local Lord & Taylor department store and a local TV station. According to King's unnamed source, the police were able to get a good look at the man's face in the video, although based on King's word choice it remains unclear whether the FBI has a name to go along with that face.
Regardless, if accurate, this would be a major development in the case given the latest official word from police was that they had no suspects.
King's mentioned several sources during his on-air reporting, although only one—someone who has been briefed on the ongoing investigation but not part of it—has confirmed police have IDed a suspect. The others have only said that police feel like they have made a significant breakthrough.
The FBI and local officials are scheduled to hold their next briefing at 5 p.m. We'll likely have to wait until then to know for sure.
This post has been updated with additional information as it became available.