The arrest is based on two videos showing images of the suspect, a federal law enforcement source told CNN contributor Fran Townsend.
[Updated at 1:46 p.m.]
An arrest has been made in connection with Monday's Boston Marathon bombings, sources tell CNN's John King and CNN contributor Fran Townsend. King's source is with Boston law enforcement, he said; Townsend's source is with federal law enforcement.
[Updated at 1:44 p.m.]
While we wait for more information about the possible suspect, some recent information about one of the three people who were killed in Monday's blasts: Boston University said Lingzi Lu, a graduate student in mathematics and statistics, was killed.
She and two friends were watching the race near the finish line when the blasts erupted, BU Today reported. The second student was in stable condition at Boston Medical Center; the third student was not hurt, it said.
The university said that it had the family's permission to identify Lingzi Lu.
[Posted at 1:40 p.m.]
Authorities may have had a breakthrough in the investigation of Monday's Boston Marathon bombings. Investigators believe they have identified a suspect, a source who has been briefed on the investigation told CNN's John King exclusively.
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.
Earlier, a federal law enforcement source with firsthand knowledge of the investigation told CNN that a lid to a pressure cooker thought to have been used in the bombings had been found on a roof of a building near the scene.