Boston authorities could have prevented last month's deadly Boston Marathon bombings if federal law enforcement agencies had adequately shared information and followed through on warnings about accused bombers Tamerlan and Dzhokhar Tsarnaev, witnesses told Congress Thursday.

"I believe that though it would not have been easy, it was possible to have prevented the terrorist attacks in Boston," former Sen. Joseph Lieberman, I-Conn., told the House Homeland Security Committee. "In a literal sense, the homeland security system we must acknowledge that we built after 9-11 to protect the American people from terrorist attacks failed to stop the Tsarnaev brothers."

In the first congressional hearing into the April 15 bombing that killed three and injured more than 200, Lieberman and other witnesses testified about a lack of information sharing between federal agencies and between federal authorities and local police. Republicans and Democrats alike joined in the criticisms.

"We cannot ignore that once again it has taken a tragedy to reveal problems in our vast, varied and numerous federal databases," said Rep. Bennie Thompson, of Mississippi, the committee's top Democrat.

Witnesses told the committee that Boston authorities were never told prior to the bombing that Russia had warned the FBI about the older brother, Tamerlan Tsarnaev, the bombings' alleged mastermind who also had posted radical jihadist videos on the internet.

The FBI, in turn, was unaware that the older brother had returned to his home region near Chechnya, where he is believed to have met with Islamic extremists who helped radicalize him.

"In other words, he was on our radar screen, and then he was off," said Lieberman, a former chairman of the Senate Homeland Security Committee.

Boston Police Commissioner Edward Davis told lawmakers that neither he nor the city's four-person Joint Terrorism Task Force had been told of Russia's explicit warnings to U.S. officials about Tamerlan or the investigation the FBI had opened on the brother. Those lapses meant local police knew nothing about the brothers or the dangers they posed prior to the homemade bombs going off at the marathon's finish line, he said.

Dzhokhar and Tamerlan Tsarnaev, immigrants from Chechnya, are accused of setting off two bombs made from pressure cookers that killed three people and injured 264. The attack spawned a massive manhunt that resulted in Tamerlan being shot and killed by police in Watertown, Mass. His brother, Dzhokhar, fled the scene of the shooting in a stolen SUV only to be found four days after the bombing hiding in a parked boat in Watertown.

Dzhokhar was hospitalized with multiple gunshot wounds and later charged with using a weapon of mass destruction and malicious destruction of property resulting in death.

In questioning Dzhokhar, police learned that the brothers were planning another attack, this time on New York City. But New York lawmakers said the FBI also failed to alert them to the danger.

"I think it's absolutely indefensible that the FBI found out on Sunday that there was a planned attack against Times Square and never notified the NYPD," Rep. Peter King, R-N.Y., said at the hearing. "Here's a city that's been attacked twice, had 16 plots against it, and the FBI refused to give that information to the NYPD."