Three men were arrested on charges that they helped Boston Marathon bombing suspect Dzhokhar Tsarnaev after the deadly attacks last month.

Federal prosecutors allege that Dias Kadyrbayev, 19, and Azamat Tazbayakov, 19, tried to conceal and destroy a laptop and backpack full of fireworks belonging to Tsarnaev, a friend from the University of Massachusetts Dartmouth, where they were all students at one time. They were charged with alleged conspiracy to obstruct justice by the U.S. Attorney's office in Massachusetts.

A third man, Robel Phillipos, 19, was accused of lying to law enforcement officials who questioned him about the bombing.

Kadyrbayev and Tazbayakov live in New Bedford, but are originally from Kazakhstan. They were already accused of violating the terms of their student visas.

Phillipos is from Cambridge, the same city where Tsarnaev grew up and attended UMass-Dartmouth with the others.

The Boston Police Department had announced earlier on Wednesday via Twitter that new suspects were in custody.

"Please be advised that there is not a threat to public safety," the police announced in a statement. "There is no additional info to release at this time. Additional details will be provided when they become available."

Tsarnaev, 19, was a student at the University of Massachusetts - Dartmouth at the time of the bombing.

An FBI agent's affidavit explained how Tsarnaev's three friends discovered his alleged role in the bombing and the steps they took to conceal it.

Phillipos called Kadyrbayev to say that Tsarnaev resembled one of the suspects in the photos released by the FBI on April 18, the affidavit said. Kadyrbayev sent text messages to Tsarnaev joking about the physical similarities. Tsarnaev wrote back saying "lol" and "you better not text me," which Kadyrbayev didn't take seriously, the affidavit said.

The three friends met in Tsarnaev's dorm room that night even though he wasn't there, according to Kadyrbayev's statements. While watching a movie, they noticed a backpack containing fireworks that had been emptied of the explosive powder.

"Kadyrbayev knew when he saw the empty fireworks that Tsarnaev was involved in the Marathon bombing," Agent Scott Cieplik swore in his affidavit. He then "decided to remove the backpack from the room in order to help his friend Tsarnaev avoid trouble."

He also took Tsarnaev's laptop, because he thought it would appear less suspicious to Tsarnaev's roommate, who was also in the dorm room. Tzahayakov told authorities that they also took a jar of Vaseline, which they believed might have been used to produce bombs.