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After an initial blast, a second explosion appears in the background near the finish line of the Boston Marathon.Getty Images

Investigators say they are following strong leads in identifying suspects behind the Boston marathon bombings, after a study of video footage near the finish line.

Both cellphone and surveillance video were reportedly used to identify possible suspects, the Boston Globe reported.

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According to reports, a suspect was seen carrying and possibly dropping a black bag outside of a restaurant on Boylston Street, the site of the second bombing.

"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 Globe. "All I know is that they are making progress."