From Yahoo.com :

Boston police have three additional suspects in custody in connection to the Boston Marathon bombings, the department confirmed to Yahoo News Tuesday.

A spokeswoman at the Boston police department directed all questions on the suspects to the FBI, which has yet to disclose their identities.

Dzhokhar Tsarnaev, a 19-year-old college student, is charged with killing three and injuring more than 200 in the two bombs last month. His older brother, Tamerlan Tsarnaev, was killed while fleeing arrest.