Investigators are trying to piece together Shahzad's movements after he left an explosives-laden SUV in the center of New York City's bustling theater district Saturday night, including whether anyone helped him.
CBS News.com Special Section: Terrorism in the U.S.
Anyone who might have aided Shahzad may have done so unwittingly, without knowledge of the plot, the sources said.
Authorities are also still for the attack, such as religion, hatred of Americans or money, sources said.
Shahzad was originally scheduled to be arraigned on terrorism and weapons of mass destruction charges Wednesday, but his court appearance has been delayed.
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