(CNN) -- A federal grand jury Thursday charged two friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev with obstructing justice and conspiracy to obstruct justice, the U.S. attorney's office in Boston said. 

Azamat Tazhayakov and Dias Kadyrbayev -- 19-year-old roommates and Kazakh nationals who began attending the University of Massachusetts-Dartmouth the same semester as Tsarnaev -- were charged in May with conspiracy. 

It is not clear whether Thursday's indictment represents a second conspiracy charge. 

Thursday's indictment accuses Tazhayakov and Kadyrbayev of helping Tsarnaev after the April 15 bombing by taking items from his dorm room to keep them from investigators. 

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If convicted, Tazhayakov and Kadyrbayev could be sentenced to a maximum 20 years in prison on the obstruction count and up to five years on the conspiracy count, the U.S. attorney's office said. They also could be fined $250,000. 

Arkady Bukh, Tazhayakov's attorney, said his client is not discouraged. He also said that Tazhayakov did not touch any of Tsarnaev's items. 

"He feels very strongly he'll be able to be able to convince a jury that's he's innocent," Bukh said. "There's no evidence of intent, no incentive to help (Dzhokhar), no motive to destroy anything." 

The three students socialized and texted each other, the indictment says. 

On April 18, three days before the FBI searched Tsarnaev's dorm room, Tazhayakov and Kadyrbayev allegedly went into the dorm, took Tsarnaev's laptop and a backpack containing Vaseline, a thumb drive, fireworks and a "homework assignment sheet" and took them back to their New Bedford apartment, the indictment states. 
WHAT IS TAZAYAKOV AND KABYRBAYEV ACCUSED OF?
obstructing justice and conspiracy to obstruct justice