The brothers Tsarnaev had plans to drive to New York in their carjacked Mercedes and explode their remaining bombs last Thursday, but their plans went off track when the owner of the car they stole made an escape, law enforcement sources told ABC News.
Authorities said the information came to the attention of investigators during the interrogation of 19-year old Dzhokhar Tsarnaev, who had at first said the plan was to go to New York to "party" but then changed his story in a subsequent interview. At that time Tsarnaev allegedly acknowledged that he and his brother planned a follow-up attack. The brothers had several unexploded devices with them as they tried to flee, Boston Police sources said.
There was no immediate reaction from New York officials but Mayor Michael Bloomberg has scheduled a news conference for this afternoon.
Law enforcement officials also tell ABC News they are preparing to move the accused Boston Marathon bomber from his hospital room to a secured medical facility in one of the region's prisons, sources tell ABC News.
The move is expected in the next 48 hours, but officials were not making public the timing of the transfer or the Tsarnaev's destination. There are several prison facilities around Boston that have medical facilities.
The developments come after authorities collected what could be fresh evidence of how the men believed responsible for the twin detonations at the Boston Marathon finish line constructed their bombs.
Agents uncovered a stash of firework shells, some of which appeared to have been emptied of their gunpowder. The cache was discovered in a used clothing collection bin in a grocery store parking lot in Watertown.