There have been conflicting reports as to whether a suspect has been arrested in the Boston Marathon bombing.
CNN reported on Wednesday that authorities arrested an unidentified suspect in the bombing based on security footage that shows a man depositing a bag at the scene before the blasts.
Later, though, the news site reported that Investigators denied that an arrest had been made, saying, however, that there has been "substantial" progress in the case.
According to the original report, the suspect was expected to appear in federal court in Boston later on Wednesday.
He was reportedly seen on surveillance footage that showed a young man carrying – and perhaps depositing – a black bag at the second bombing scene at the finish line of Monday's race, where two bombs exploded, killing three and injuring 176.
The video footage, which was taken directly across the street from one of the blasts, has reportedly provided investigators with clear video of the area.
“The camera from Lord & Taylor is the best source of video so far,” said Dot Joyce, a spokeswoman for Boston Mayor Thomas M. Menino told the Boston Globe. “All I know is that they are making progress.”
Bomb scene pictures produced by the Boston Joint Terrorism Task Force on Tuesday show the remains of an explosive device including twisted pieces of a metal container, wires, a battery and what appears to be a small circuit board.
Security officials who spoke on condition of anonymity said instructions for building pressure-cooker bombs similar to the ones used in Boston can be found on the Internet.
Pressure cookers had also been discovered in numerous foiled attack plots in both the U.S. and overseas in recent years, including the failed Times Square bombing attempt on May 1, 2010, officials said.
No individual or group has yet claimed responsibility for the attack, although it has been widely speculated that the Pakistani Taliban is to blame. A competing theory is that the attack was an act of homegrown terror timed for Tax Day.