The FBI has said it wants to speak to two men seen in at least one video from the Boston Marathon, says Homeland Security Secretary Janet Napolitano, but has not referred to them as 'suspects'.
Three people were killed and more than 170 other were injured when the bombs exploded on Monday.
Ms Napolitano told the House Homeland Security Committee today that "there is some video that raised the question" of two men the FBI would like to interview but said would not describe them as suspects. She said the investigation is continuing "apace".
New photos of the suspects identified by officials as Dzhokar A. Tsarnaev, 19 and Tamerlan Tsarnaev, 26 have been released.
The FBI has released pictures and video of two suspects in the Boston Marathon bombing, seeking the public's help.
President Obama attended a memorial service in Boston today, paying tribute to the victims of Monday's terrorist attack.