Boston Marathon Bomb Probe: Gathering Evidence

By Day 3 of their investigation, authorities scouring the bombing scene—on the ground and on rooftops—and viewing countless videos and photos of the Boston Marathon finish line were able to gather significant evidence. Here are images of some of what they found. The evidence photos were released by investigators. Meanwhile, friends and strangers remembered the victims.

Related: Day 1 Scenes From the Bombing

By CNBC.com
Posted 17 April 2013

Humvees roll down a deserted Boylston Street, where two bombs exploded Monday.

An FBI crime scene investigator places an evidence marker on Boylston Street just past Berkeley Street near the scene of the Boston Marathon bombing.

An investigator carries an evidence bag off a rooftop near the site of two explosions at the finish line of the Boston Marathon.

Part of an apparent explosive device.

Another view of the remains of what may have been an explosive device.

A piece of what's believed to be an explosive device.

A view of the battery that may have been attached to an explosive device.

A nail and two ball bearings believed to have been put inside a pressure cooker bomb device to inflict greater damage.

A close-up of the battery believed to have been used in the explosive device.

Part of a circuit board found by investigators.

While gathering evidence, investigators also inspected trash cans, apparently to make sure there were no other unexploded devices.

A woman looks at a street memorial near the scene of the bombings.

Flowers and a sign are left on a street post in Medford Square in remembrance of Krystle Campbell, 29, of Medford, who was among those killed.

A young girl cries with her mother during a Tuesday night vigil for 8-year-old Martin Richard of Dorchester. A third person who died was identified as Lu Lingzi, a Boston University graduate student from China.