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Kevin Johnson, Donna Leinwand Leger and Doug Stanglin, USA TODAY

Three friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev have been arrested on federal charges of conspiring to obstruct justice and making false statements for allegedly removing his backpack and laptop from his dorm room. Their actions came after they concluded he was involved in the April 15 attack.

None of the three are suspected of having advance knowledge of the plot or participating in the planning of the bombing, according to a law enforcement source.

Azamat Tazhayakov and Dias Kadyrbayev, both 19 and from Kazakhstan, are accused of obstruction of justice and conspiring to conceal the evidence. A third, Robel Phillipos, 19, of Cambridge, is charged with making materially false statements to federal law enforcement officials during a terrorism investigation.

The three are appearing in federal court Wednesday afternoon.

Dzhokhar Tsarnaev, 19, has already been charged in connection with the bombings that killed three people and injured more than 260. Wounded following a shootout with police, Tsarnaev is being held in a prison medical center.

According to the federal complaint, the backpack that Tazhayakov, Kadyrbayev and Phillipos found in Tsarnaev's University of Massachusetts Dartmouth dorm room contained fireworks from which explosive powder had been emptied. Investigators have said at least one of the bombs was a pressure cooker packed with explosive powder and metal parts.

According to court documents, on the night the FBI released photographs of Tsarnaev and his brother, Tamerlan Tsarnaev, the friends took Dzhokhar Tsarnaev's backpack which contained fireworks that had been emptied of gunpowder.

Kadyrbayev and Tazhayakov "admitted that they agreed to get rid of it after concluding from news reports that Tsarnaev was one of the Boston Marathon bombers,'' the documents said.

"Kadyrbayev knew when he saw the emptied fireworks that Tsarnaev was involved in the marathon bombing,'' the court documents state."According to Kadyrbayev, they then collectively decided to throw the backpack and fireworks into the trash because they did not want Tsarnaev to get into trouble.''

Kadyrbayev "decided to take Tsarnaev's laptop as well because he did not want Tsarnaev's roommate to think he was stealing or behaving suspiciously by just taking the backpack,'' the documents said.

After removing the items from Tsarnaev's room, they took them to Kadyrbayev and Tazhayakov's apartment. It was then that the three "started to freak out because it became clear from a CNN report that we were watching that (Dzhokhar) was one of the Boston Marathon bombers,'' Phillipos told investigators, according to court documents.

According to the documents, Phillipos recalled that Kadyrbayev then asked if he "should get rid of the stuff.''

Phillipos replied, "Do whatever you have to do.''

The backpack was later recovered from a New Bedford landfill, partially enclosed in a black garbage bag. Inside the pack, according to the court documents, federal agents recovered fireworks, a jar of Vaseline and a homework assignment sheet from one of Tsarnaev's classes.

Lawyers representing the two Kazakh students in immigration court Wednesday morning on unrelated visa issues said that they had cooperated with Homeland Security and FBI investigators for hours and were only college friends of Tsarnaev and should be released, The Boston Globe reported.

The two have been held in a county jail for more than a week on allegations that they violated their student visas while attending school with Tsarnaev.

Tsarnaev's 26-year-old brother Tamerlan, the other suspect in the bombings, died in a shootout with police three days after the attack. Dzhokhar was captured several hours later hiding in a boat in a backyard in Watertown, Mass.

Contributing: Gary Strauss, USA TODAY; Associated Press

Robel Phillipos complaint