BOSTON (AP) -- Three college friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev were arrested and accused Wednesday of removing a backpack containing hollowed-out fireworks from Tsarnaev's dorm room three days after the attack to keep him from getting into trouble. In court papers, the FBI said one of them threw the backpack in the garbage -- it was later found in a landfill by law enforcement officers -- after the young men concluded from news reports that Tsarnaev was one of the bombers. Azamat Tazhayakov and Dias Kadyrbayev, both 19-year-olds from Kazakhstan, were charged with conspiring to obstruct justice by concealing and destroying evidence. Robel Phillipos, 19, who graduated from the prestigious Cambridge Rindge and Latin High School with Tsarnaev, was charged with lying to investigators about the visit to Tsarnaev's room. The three were not accused of any involvement in the bombing itself. But in a footnote in the court papers outlining the charges, the FBI said that about a month before the bombing, Tsarnaev told Tazhayakov and Kadyrbayev that he knew how to make a bomb. The lawyers for the Kazakh students said their clients had nothing to do with the bombing and were just as shocked by the crime as everyone else. Phillipos' attorney, Derege Demissie, said outside court: "The only allegation is he made a misrepresentation." At a court appearance in the afternoon, the Kazakh students did not request bail and will be held for another hearing May 14. Phillipos was held for a hearing on Monday.