On Tuesday morning officials said that the only explosive devices found were the ones that exploded at the marathon — clarifying conflicting statements that were given Monday in the chaotic aftermath of the blast, when some law-enforcement officials had said that other devices were found. “There were no unexploded devices found,” Gov. Deval Patrick said Tuesday morning.
Representative Michael McCaul, a Texas Republican who heads the House Homeland Security Committee, said the authorities believe that the explosives were similar to improvised explosive devices that have been used against American troops in Iraq and Afghanistan. Mr. McCaul, a former federal prosecutor who received briefings Tuesday morning from the Federal Bureau of Investigation and Homeland Security officials, also said that the authorities still did not know whether the attack was a foreign or domestic plot.
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.