BOSTON (AP) — An FBI agent says that two friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev (joh-HAHR' tsahr-NEYE'-ehv) would have been arrested if they did not come to a police station voluntarily.

Special Agent John Walker testified in federal court on Wednesday that Dias Kadyrbayev (DY'-us kah-dur-BY'-ehv) and Azamat Tazhayakov (AZ'-maht tuh-ZAY'-uh-kahv) were brought in for questioning willingly four days after the attack. Both were held in handcuffs.

Walker said that the two men had to be questioned because they might know the whereabouts of a dangerous fugitive. He also added that they were Kazakhstan nationals in the U.S. illegally.

Kadyrbayev's attorney says his client was not interrogated willingly. He wants Kadyrbayev's testimony kept out of his upcoming trial.

Kadyrbayev is charged with tampering with evidence for removing Tsarnaev's laptop and a backpack from his dorm room.