May 2, 2010 -- The would-be car-bomber who left an SUV loaded with propane and gas cans, fireworks and timing devices on a Times Square street also had more than 100 pounds of fertilizer, but not the kind that would explode, police said today.

Instead of ammonium nitrate, the kind of fertilizer used by Oklahoma City bomber Timothy McVeigh, the person who abandoned the van on the crowded New York City street had a metal gun locker full of a harmless fertilizer, New York City Police Department spokesman Paul Browne said.

While it is unknown who the potential bomber is, or the bomber's motive, officials told ABC, that if that person were not aware of the characteristics of the fertilizer it could point to the fact that the bomber did not know what he was doing.

Sources also told ABC News that the valves on the propane tanks were not open, which would have made it less likely that the gas inside would have ignited.

Police are looking for white male in his 40s who was seen leaving the area near the SUV and shedding a dark shirt, revealing a red shirt underneath, about a half block from where survellance cameras saw the vehicle entering Times Square at about 6:28 p.m. Saturday, NYPD Commissioner Ray Kelly said.

The video of the possible suspect was expected to be released later today.

The individual was looking around in a furtive manner, Kelly said, but he also stressed that the behavior could be totally innocent.

At a Sunday afternoon press conference, Kelly said police would be reviewing hundreds of hours of videotape, and that police had identified the owner of the green Nissan Pathfinder but had not yet spoken to them.

Detectives are in Pennsylvania today meeting with tourists who think they may have captured a suspect on video.

Kelly said "no evidence" supports the Pakistani Taliban's claim of responsibilty for the bombing, but he said investigators had not yet ruled out either domestic or international motives for the attempted attack.

"Clearly it was the intent of whoever did this to cause mayhem and create casualties," Kelly said. "It was just a sober reminder that New York is clearly a target of people who want to come here and do us harm."

At about 2 p.m. Sunday, NYPD opened the 55-by-32-inch gun locker that was inside the SUV and found it contained eight bags of an unknown, fertilizer-like substance and an inverted pot with a "bird's nest" of wires.

There were three propane tanks next to the gun locker, two five-gallon jerry cans of gasoline, and a timing device, police officials said. There was no high-grade explosive, and the timing device was clocks attached to wires. Attached to the propane tanks were M88 fireworks, some of which had gone off, but without igniting the gas.

One alarm clock appeared to be wired into the gun locker. Another alarm clock was wired to a can with up to 30 M88 firecrackers resting between the cans of gasoline.

Kelly said it was too early to determine whether the device was crude or not.

"The system was workable," he said. "The materials are in doubt."

In response to the incident, the Transportation Safety Administration began some additional security measures at East Coast airports this morning. Many of the actions focused on vehicle-borne devices and other improvised devices and included more bomb-sniffing dog sweeps and vehicle checks.

The Department of Homeland Security also provided intelligence to federal air marshals for domestic and international flights and to customs and border officials. A bulletin summarizing the incident was also sent to the nation's 18,000 law enforcement agencies.

Times Square Car Bomb -- Tracking the Vehicle

The Connecticut license plate on the car does not match the vehicle, and investigators have spoken to the individual to whom the plates are registered, according to Kelly.

That license plate ultimately was traced to a Connecticut junkyard, officials said.

The car bomb was discovered when a T-shirt vendor saw something suspicious -- smoke coming from an unoccupied SUV on 45th Street near 7th Avenue -- so he alerted police.

The tip led to what New York Mayor Michael Bloomberg called an "amateurish"-looking car bomb that Secretary of Homeland Security Janet Napolitano told ABC News' "This Week" might have been part of a "one-off" attack.

The 6:30 p.m. scare prompted police to evacuate thousands of people from the heart of the Big Apple during one of its busiest times -- a warm Saturday night when it was packed with theatergoers and tourists.

"We are very lucky," Bloomberg said. "Thanks to alert New Yorkers and professional police officers, we avoided what could [have been] a very deadly event."

Authorities were examining security cameras and other evidence to see if they could identify a possible suspect or motive -- and already had located video of the car being driven to the scene.

"Right now, we have no evidence that this was anything but a one-off" attack, Napolitano told "This Week" this morning.

"Tape is being reviewed and additional forensics are being done in addition to that," she added. "Times Square, I think, now is safe."

President Obama was being kept informed on the investigation by Deputy National Security Advisor John Brennan, who was communicating with the New York Police Department and other investigators, the White House announced Saturday evening.

"This is a bomb. This is a car bomb -- a crude device that includes gasoline, propane and is wired together," Browne said Saturday night.

"The wiring ... looked amateurish, I think, is a nice way to phrase it," Bloomberg added early today. "It was made up of consumer-grade fireworks that you can buy in Pennsylvania and drive into New York.

"It certainly could have exploded and had a pretty big fire, and a decent amount of explosive impact," Bloomberg said.

Richard Clarke, a former counterterrorism czar under Presidents Clinton and Bush, told ABC News' "Good Morning America" that he expects to see an arrest in the case.

"You can be pretty certain this guy will be found," he said, "because of all the videotapes, because the bomb not [fully] going off left a wealth of evidence."

He suggested the incident shows how an alert populace can help foil an attack.

"It's a reminder to all of us, whether we're in airports or train stations, subways, if we do see something that looks a little suspicious, it's much better to call it in than to have the guilt afterwards that you didn't," Clarke said.

'See Something, Say Something' Is a Security Mantra That Worked

The T-shirt vendor, who's a Vietnam veteran, noticed smoke coming from the vehicle at around 6:30 p.m. Saturday and notified a mounted police officer.

"It was just sitting there and there was nobody sitting there and the hazards were on and nobody's in there," said another vendor, Rallis Gialaboukis, who saw the whole thing. "I think that by putting the hazards on might have made people think that it was stalled or it was overheating."

The mounted officer noticed a smoking box in the back of the Nissan Pathfinder, police said.

The New York Police Department's bomb squad was called in, and the back window of the SUV was broken out. Police sent in a robot to determine what was in the vehicle.

While the bomb squad robot was checking out the vehicle, the NYPD quickly blocked off 44th Street through 48th.

Bomb technicians from the FBI's New York office were called to the scene to assist the NYPD Bomb Squad in the investigation.

Shortly after 7 p.m., witnesses told WABC-TV they heard an explosion, then saw smoke coming from the car.

"It was a boom and a puff of smoke," one man said.

"I saw people running, turning tables," Paula Delarrosa said.

A live webcam feed at 46th Street and Broadway Saturday evening showed the streets had been cleared of pedestrians. A line of police cars blocked one street and officers paced on a sidewalk.

In the hours that followed, Broadway remained empty.

"I came to dinner," said visitor Tony Rosenthal. "We were going to go see the show 'Come Fly Away' at the Marquis Theater, and the street's closed. I don't know if we'll be able to see the show."

Another observer, Joy Adler, said, "It's pretty scary. I mean, this is really scary. You hear about it on TV and to actually see it, very scary."

Times Square Bomb Similar to London Cases?

The New York case may not be the first of its type, Clarke told "Good Morning America."

Days before an attempted car bomb attack at an airport in Glasgow, Scotland in June 2007, devices similar to the one in New York, using propane tanks and gasoline, were planted in two cars in downtown London but failed to explode.

"In that case, it was made by Islamic jihadists who were not part of the al Qaeda but had learned about al Qaeda, studied it on the Internet, learned how to make the bomb on the Internet," Clarke said.

As in New York, the first London vehicle was discovered when a passerby noticed smoke coming from the back seat of the vehicle. The other car unwittingly was towed for being parked illegally and the bomb was discovered later.

ABC News' Ron Claiborne, Jim Sciutto and Aaron Katersky contributed to this report