Boston Marathon bomber Tamerlan Tsarnaev passed the U.S. citizenship test just three months before he and his younger brother, Dzhokhar Tsarnaev, set off explosives at the finish line on April 15, 2013, the Boston Globe reported late Sunday, citing federal immigration records obtained under the Freedom of Information Act. The documents were released after questions were raised over the immigration process that it may have missed warning signs about the duo's criminal activity.

The immigration documents that contained Tamerlan Tsarnaev’s test results are reportedly in 651 pages of previously confidential files on the bomber and his friend Ibragim Todashev. The U.S. Department of Homeland Security provided redacted files, which had only 206 pages in their entirety, to the Boston Globe after several requests over a span of three years.

“U.S. Citizenship and Immigration Services’ (USCIS) commitment to national security is shared inside and outside of the Department of Homeland Security,” the agency reportedly said, in a statement released Sunday saying that the cases were processed correctly. “While USCIS found no errors in the processing of Tamerlan Tsarnaev’s or Ibragim Todashev’s applications, we are always seeking to strengthen our very intensive screening processes.”

According to the now-disclosed records, Tamerlan Tsarnaev went to the John F. Kennedy Federal Building in Boston months before the bombings to swear allegiance to the United States, the Boston Globe reported. He also denied any links to terrorism. The records also stated that Todashev told immigration officials that he had left Massachusetts in September 2011, the same month he was allegedly involved in the brutal slayings of three men in Waltham, Massachusetts, along with Tamerlan Tsarnaev.

Tamerlan Tsarnaev was killed during a gun battle with police after the Boston bombings that killed three people and injured more than 260 others. Todashev was killed by an FBI agent during an interrogation in Florida, a month after Tamerlan Tsarnaev’s death.

Last year, Dzhokhar Tsarnaev, 22, was sentenced to death after he was found guilty on all 30 charges against him for his role in the 2013 Boston Marathon bombing.

The immigration files do not show any security concern about Tamerlan Tsarnaev or Todashev, but instead show the two as ethnic Chechens from Russia, struggling with unemployment and poverty while trying to make their future in the U.S. Tamerlan Tsarnaev wanted his ties with the U.S. through citizenship and Todashev through a green card. The two were so poor that the government also waived their immigration application fees, officials said, according to the Boston Globe.

In his immigration application, Tamerlan Tsarnaev had expressed his interest to change his first name Tamerlan to that of an early Islamic scholar, Muaz, something that authorities said should have raised concern among the officials. He had also disclosed a 2009 arrest for assaulting a former girlfriend, and that he was receiving government benefits and had recently traveled overseas.

Despite correct answers to questions on English and knowledge of U.S. history and government, the officer checked the next box, which said, “A decision cannot yet be made about your application.” The documents did not reveal the reasons for the delay. Earlier, a federal report said that Tamerlan Tsarnaev’s citizenship application was delayed because the government did not have his criminal court records from the 2009 case.