(Boston, MA)  --  Authorities in Boston are preparing to conduct a controlled explosion as large parts of the area remain under lockdown.  Law enforcement from multiple agencies are combing through the streets of Watertown in hopes of tracking down 19-year-old bombing suspect Dzhokhar Tsarnaev.  Massachusetts Governor Deval Patrick advised residents to stay indoors and only open doors for uniformed law enforcement.  Investigators say they are following up on several important leads.  

The FBI believes Tsarnaev played a role in planting the bombs that ripped through crowds at the Boston Marathon Monday, killing at least three and injuring more than 170.  Another suspect in the bombing was killed in a shootout with officers overnight.