In a major development in the Boston Marathon bombings probe, three 19-year-old students, including two Kazakhs, were arrested today by the FBI and charged with covering up for the suspected bombers.

Dias Kadyrbayev and Azamat Tazhayakov, both of New Bedford in Massachusetts, were charged in a criminal complaint with conspiracy to obstruct justice by conspiring to destroy, conceal and cover-up tangible objects belonging to Dzhokhar Tsarnaev, the main accused in the attacks along with his slain brother Tamerlan, 26.

Tazhayakov and Kadyrbayev, are Kazakh nationals and have been charged with destroying, concealing and covering-up objects belonging to Dzhokhar, namely a laptop and backpack containing fireworks, US Attorney Carmen M. Ortiz said in a statement.

A third man, Robel Phillipos, of Cambridge, Massachusetts has been charged with wilfully making materially false statements to federal law enforcement officials during a terrorism investigation. He is a US citizen.

The three 19-year-olds were classmates of Dzhokhar, who has been charged with the conspiracy to use weapons of mass destruction.

The Federal Bureau of Investigation (FBI) arrested them in connection with the Boston marathon bombings that killed three people and injured more than 250 others in the worst terrorist attack on the American soil since 9/11.

According to the affidavit accompanying the complaint, Kadyrbayev and Tazhayakov are both nationals of Kazakhstan who entered the US on student visas.

Kadyrbayev and Tazhayakov face a maximum sentence of five years in prison and $250,000 fine.

Tazhayakov and Kadyrbayev have been held in jail since April 20 on allegations that they violated their student visas while attending the University of Massachusetts at Dartmouth with Dzhokhar.

Phillipos, faces a maximum sentence of eight years in prison and a $250,000 fine.

“Please be advised that there is not threat to public safety. Three additional suspects have been taken into custody in connection to the attack on the Boston Marathon,” the Boston police department had said earlier in a statement uploaded on Twitter.