Security officials face questions over Boston Marathon bombings

(Reuters) - Top 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.

Prosecutors say he and his elder brother Tamerlan Tsarnaev, 26, carried backpacks containing pressure cooker bombs that ripped through the crowd near the finish line of the world-renowned race on April 15, killing three people and wounding more than 200.

Tamerlan Tsarnaev was shot in an exchange of gunfire with police and run over by his younger brother early on Friday, police said. He later died at a hospital. Dzhokhar Tsarnaev fled on foot but was captured later that day following a massive manhunt.

Russian authorities flagged the elder Tsarnaev in 2011 as a possible Islamist radical, and some lawmakers have accused the FBI of failing to act thoroughly enough after Russia's security services raised their concerns. The FBI questioned him in 2011.

Top investigators were slated to brief the full House of Representatives on Tuesday about the failure to spot the danger.

Dzhokhar Tsarnaev told investigators in his hospital room that he and his brother acted alone, without any help, according to reports by CNN and the New York Times. He said his older brother was the driving force behind the bombings, according to CNN.

The Times reported that he admitted to the bombings in questioning by investigators on Sunday. These reports could not be independently confirmed.

The younger Tsarnaev, an ethnic Chechen who is a naturalized U.S. citizen, will be tried in a civilian rather than a military court. Some Republican lawmakers had called on the Obama administration to designate him as an enemy combatant, which would have restricted his rights.

Evidence against him is now likely to be presented to a grand jury by prosecutors who will seek a formal indictment.

Both charges against Tsarnaev carry the possibility of the death penalty. Given the apparent evidence against him, plea negotiations are likely, legal experts said.