Proposed changes to the nation's immigration laws would have made it easier to track one of the suspects in the Boston Marathon bombings before the attack, the nation's homeland security chief said Tuesday.

Homeland Security Secretary Janet Napolitano. (AP)

Homeland Security Secretary Janet Napolitano also confirmed that federal agencies didn't  initially notice that one of the two suspected bombers, Tamerlan Tsarnaev, had left the country last year on a six-month trip to Russia because his name was misspelled on his airline ticket. Other unspecified "redundancies" eventually alerted federal agencies that Tsarnaev had left the country, she said.

Speaking at a Senate Judiciary Committee hearing on proposed changes to immigration laws, Napolitano noted that the bipartisan plan would require that all U.S. passports be electronically readable and would reduce the likelihood of potential mistakes.

The bill "really does a good job of getting human error, to the extent it exists, out of the process," she said.

Napolitano appeared before the Judiciary panel Tuesday morning after canceling an appearance last Friday as she tracked the manhunt for the Tsarnaev brothers.

Tamerlan Tsarnaev, 26, died early Friday after a shootout with police officers in Watertown, Mass., while Dzhokhar Tsarnaev, 19, who is recovering from serious injuries at a Boston hospital, was formally charged Monday with using a "weapon of mass destruction."

Since the bombings, the FBI has said that it investigated Tamerlan Tsarnaev's possible link to terrorist groups at the request of Russia. The FBI had closed its investigation into Tsarnaev by the time he returned to the United States last year, Napolitano said.

During the hearing, Napolitano also clarified that a Saudi man questioned in the hours after the bombings was not on the U.S. terrorist watch list before the bombings, but was temporarily added to the list as he was questioned by law enforcement officials.

The Saudi man "was in the wrong place at the wrong time," Napolitano said. "He was never a subject. He was never even really a person of interest." The man was removed from the terrorist watch list after he was questioned, she added.

Members of the House of Representatives are scheduled to receive an FBI briefing on the Boston bombings and subsequent investigation Tuesday afternoon. A classified briefing for members of the Senate Intelligence Committee is scheduled for Thursday afternoon.

Napolitano's appearance Tuesday followed a testy exchange Monday during which Democrats on the Judiciary panel chastised Sen. Charles E. Grassley (R-Iowa) and other Republicans for tying last week’s Boston attack to the debate over a comprehensive immigration bill.

But that didn't stop GOP senators from making the point again Tuesday. Grassley said that if the Tsarnaev brothers used the U.S. immigration system to assist their attacks, "it's important to our ongoing discussion."

The Boston bombings and the recent discovery of a Canadian terror ring, "are reminders that our immigration system is directly related to our sovereignty and national security matters," Grassley said. "For example, we know that the 9/11 hijackers abused our immigration system by overstaying their student visas. We also know that people enter legally and stay below the radar."

Napolitano also told senators Tuesday that she personally would prefer that the bill not earmark $1.5 billion to continue constructing a fence along the U.S.-Mexico border.

"We would prefer having money not so designated so that we can look at technologies -- they can be ground-based, air-based, what-have-you, manpower, other needs -- that may be more fitting to actually prevent illegal flows across the southwest border," Napolitano said. "So if we had our druthers, we would not so designate a fence fund."

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