A friend of the man accused of detonating two pressure-cooker bombs at last year’s Boston Marathon was convicted on Tuesday by a federal jury in Boston of lying to F.B.I. agents during their investigation of the attack.

On the sixth day of deliberations, the jury found Robel Phillipos, 21, guilty of two counts of lying to F.B.I. agents when they asked whether he had been in the University of Massachusetts-Dartmouth dormitory room of Dzhokhar Tsarnaev, who is charged in the bombings, as two other friends removed potential evidence.

The material removed included a computer and a backpack containing fireworks tubes, some of which had been emptied of their powder, the authorities said. “He lied to agents when he could have helped. He concealed when he could have assisted,” Carmen M. Ortiz, United States attorney for the district of Massachusetts, said Tuesday in a statement.

The two other friends who were in Mr. Tsarnaev’s dorm room — Dias Kadyrbayev and Azamat Tazhayakov — are awaiting sentencing on obstruction of justice charges.