BOSTON (Reuters) - Top U.S. security officials face a grilling from lawmakers on Tuesday over whether authorities who have charged one man with the Boston Marathon bombings may have overlooked warning signs two years ago flagging the other suspect.

Dzhokhar Tsarnaev, 19, was formally charged with using a weapon of mass destruction and malicious destruction of property resulting in death at a bedside hearing on Monday in his hospital room, where he was recovering from gunshot wounds suffered in shootouts with police.