It would be "premature" to say an attempted car bombing in Times Square wasn't an act of organized terrorism, Homeland Security Secretary Janet Napolitano said Monday.

Napolitano said the government was pursuing every possible lead into the attempted attack in the heart of Manhattan on Saturday night, and released tape overnight showing a white male in his mid-40s walking away from a SUV rigged to blow up using crude explosives and accelerants.

But after saying on Sunday that the attempted attack appeared to be a "one-off," Napolitano cautioned against definitively ruling out any possible motivation or support behind it.

"Right now every lead has to be pursued," Napolitano said on NBC's "Today" show. "We would caution against premature decisions one way or another.

"I think it's premature to rule in or rule out," Napolitano added when asked whether she could rule out whether the incident was an organized act of terror. "The investigation needs to now take its course."