BOSTON (AP) — The work to identify a bombing suspect from reams of Boston Marathon footage has yielded a possible breakthrough as investigators focus on a man seen dropping off a bag near the site of the second of two deadly explosions.

City Council President Stephen Murphy says investigators saw the image of the man dropping off a bag and matched the findings with witness descriptions of someone leaving the scene. He says he was briefed by Boston police.

President Barack Obama is planning to attend a service honoring the victims Thursday in Boston, where the bombings three days earlier killed three people and wounded more than 170.

Massachusetts Gov. Deval Patrick said he understands frustration that no suspects have been captured, but he said it takes time to complete a thorough investigation.

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(Photo: AP Photo/Elise Amendola)