ROUGH CUT-NO REPORTER NARRATION

STORY: President Barack Obama called the Boston Marathon bombings an "act of terror" on Tuesday and investigators said no additional explosive devices have been found other than two that detonated near the finish line, a development that could complicate the case.

Law enforcement officials, who asked the public to turn over any photos or video of Monday's marathon and the blasts, did not disclose any possible leads in the investigation. No one has been arrested, police said.