The Joint Terrorism Task Force assigned to the case is examining international telephone records "between some of the people who might be associated with this and folks overseas," a senior Obama administration official told The Washington Post Monday.
Other physical evidence indicating an international angle to the failed car-bomb plot is also being examined by authorities, the Post said.
The registered owner of the Nissan Pathfinder in question told authorities he sold it for cash via Craigslist "several weeks ago."
The SUV -- packed with gasoline, propane, firecrackers, simple alarm clocks and eight bags of a non-explosive grade of fertilizer -- was abandoned in Manhattan's bustling theater district.
Authorities are still searching for two people who appeared on videotape Saturday for questioning.
One individual was shown changing his shirt in a nearby alley Saturday night, although at this point he is only a person of interest. "It looks like he was just taking off his shirt because he was hot," one law enforcement official told the Post.
The second person was seen running from the area.
"These are not suspects," New York Police Commissioner Ray Kelly said of the two individuals being sought. "These are people we would like to speak to."
During an appearance on NBC's "Today" show, Mayor Michael Bloomberg cautioned that people authorities want to interview may not turn out to be suspects.
"There are millions of people that come through Times Square," he said. "We're exploring a lot of leads."
The SUV hadn't been reported stolen but its license plate was traced to a different car being repaired in Stratford, Conn., Kelly said.
Police said they lifted some fingerprints from the SUV, the Daily News said.
Kelly said experts are investigating why the bomb didn't go off. The bomb was primitive but if it had detonated there would have been "a significant ball of fire" he said.
"I would say that was intended to terrorize, and I would say that whoever did that would be categorized as a terrorist," White House spokesman Robert Gibbs said.
Officials said a motive hadn't been determined.