Investigators Have 'Active Leads' in Bomber Hunt

Within minutes of the explosions at the Boston Marathon yesterday, authorities were already mobilizing their investigation. Evidence teams with Boston's Joint Terrorism Task Force moved to secure the bomb site, looking for timing mechanism springs, chemical residues, and other potential evidence, Time reports. FBI and CIA specialists, meanwhile, began searching their databases for clues and the Internet for congratulatory militant chatter. So far, officials tell CNN they "have a number of active leads and some good early progress in the forensics analysis." Here's what you need to know about the search so far:

• FBI and ATF agents and bomb technicians searched a Revere home on a lead related to the Saudi student officers questioned in the hospital. But CNN notes that cops say that doesn't imply they have a suspect, and that the search was consensual and thus conducted without a warrant.
• Authorities are also checking area surveillance cameras, hoping to find footage of the culprit planting the bombs. So far, they haven't found any.
• Contrary to initial reports, Gov. Deval Patrick today said emphatically that no unexploded devices had been found. Such devices would likely have provided a trove of evidence.
• "There are no known additional threats," says the FBI special agent in charge of the Boston Division; the bureau is taking the lead in the investigation, and "the citizens of Massachusetts and the City of Boston should expect to see the FBI and its JTTF partners conducting investigative activity" in the area.
• The Justice Department has a looming decision in the case: Should it treat it as a domestic terror case or an international one? The latter would give authorities access to more expansive surveillance and evidence gathering powers, thanks to FISA.
• If authorities decide there is still an imminent threat of an attack, they can question any suspect they do catch without reading his or her Miranda rights.
• Police are urging anyone with information or video from the scene to call 1-800-494-TIPS.

(More FBI stories.)