Atlanta’s WAGA-TV Tuesday obtained exclusive photos showing pieces of what are believed to be the pressure cooker used to make one of the two bombs that killed three people and injured more than 170 at Monday’s Boston Marathon.

WAGA-TV, the Fox affiliate in Atlanta, reported:

The crime scene pictures obtained by the FOX 5 I-Team show pieces of a stainless steel pressure cooker with an Underwriters Laboratory number. One picture shows the imprint: Gas and Electric.
Another picture shows what appears to be a black, padded knapsack or duffel bag. …
The FBI had no comment about the crime scene photos.
[S]ources say these and more pictures have been distributed to key investigators involved in the bomb investigation. Now, agents will identify where all the various components were manufactured, and then sold, hoping the trail leads them to the killer or killers.

Boston NBC affiliate WHDH-TV obtained photographs showing a bag near the location of the second blast that may be the bomb used in the attack:

Photos sent to 7News by a viewer show the scene just before and right after the bombs went off on Boylston Street.
7News has provided these pictures to the FBI as they continue their investigation. They are looking at the pictures to see if it’s possible it could be the second bomb.
In the first picture you can see a bag next to a mailbox and up against a barricade along the marathon route. In the second, which we have blurred because it is very graphic, there is no sign of the bag.

The use of pressure-cooker bombs has been advocated by al-Qaeda, the New York Times reported:

The explosives that killed three people and injured more than 170 during the Boston Marathon on Monday were most likely rudimentary devices made from ordinary kitchen pressure cookers, except they were rigged to shoot sharp bits of shrapnel into anyone within reach of their blast and maim them severely, law enforcement officials said Tuesday. …
Law enforcement officials said the devices were probably hidden inside dark nylon duffel bags or backpacks and left on the street or sidewalk near the finish line. Forensic experts said that the design and components of the homemade devices were generic but that the marking “6L,” indicating a six-liter container, could help identify a brand and manufacturer and possibly lead to information on the buyer. …
The scale of the attack and the crude nature of the explosives, coupled with the lack of anyone claiming to have been the perpetrator, suggested to experts that the attacker could be an individual or a small group rather than an established terrorist organization. …
Nonetheless, a senior law enforcement official said that authorities were also looking into connections between pressure cookers and Al Qaeda in the Arabian Peninsula, the Qaeda franchise in Yemen, largely because the design of the explosive device was described in a 2010 issue of the group’s online English magazine, Inspire.
“The pressurized cooker is the most effective method,” the article said. “Glue the shrapnel to the inside of the pressurized cooker.” The article was titled “Make a Bomb in the Kitchen of Your Mom.” ….
Rudimentary explosive devices made from pressure cookers have been widely used in attacks in Afghanistan, India, Nepal and Pakistan, all countries where the cooking device is common, according to a Department of Homeland Security warning notice issued in 2010.
But they have occasionally turned up in attacks in the United States as well:Faisal Shahzad, an American citizen who attempted a car-bomb attack on Times Square in May 2010, had a pressure cooker loaded with 120 firecrackers among the improvised explosives in his S.U.V. The devices smoked but never exploded.

At a Tuesday afternoon press conference, the FBI and other law-enforcement officials in the Joint Terrorism Task Force appealed to the public for tips that could lead to suspects in the Boston attack. Authorities told reporters that a student from Saudi Arabia, who fled the scene of the bombings and was identified as a “suspect” in some media accounts, is not actually a suspect. As of Wednesday morning, there had been no arrests in connection with the bombings, and the perpetrators are still at large.