Federal officials and Boston police say no arrests have been made in connection with the deadly bombings at the Boston Marathon, dismissing earlier media reports that a suspect was in custody.
Law enforcement sources, however, did say investigators believed they have identified a suspect from security video, and an official statement was expected later on April 17.
Earlier on April 17, CNN and "The Boston Globe," citing sources, said security video showed a man depositing a bag at the bomb scene before the blasts that killed three people and injured more than 170.
Investigators have said they believe the blasts may have been caused by metal "pressure-cooker" devices that were carried in dark-colored bags or backpacks.
FBI Special Agent Rick DesLauriers said investigators had recovered items from both blast sites, including pieces of black nylon that may be from a bag that may have hidden the bombs.
He said the bombs may have been built using a pressure-cooker device, and that fragments of steel pellets and nails from the bombs had been recovered.
News broadcasts have shown crime-scene photographs of what appeared to be twisted pieces of a metal container and remnants of a torn black bag.
An Al-Qaeda branch in Yemen published an online article in 2010 describing techniques for producing pressure-cooker bombs, and such bombs have been used in Pakistan, Afghanistan, India, and Nepal.
But instructions for building pressure-cooker bombs are available on the Internet and could be made relatively easily and cheaply by anyone, including a domestic terrorist.
Based on reporting by CNN, Reuters, and AFP