The NYPD is looking for two thieves who may have prevented a bombing

New York bombing suspect Ahmad Khan Rahami is now in police custody but authorities are still trying to track down two other men who may have unwittingly played a role in planting — and perhaps disabling — a bomb that failed to detonate in Manhattan on Saturday.

The men are two thieves who stole a rolling suitcase that Rahami allegedly left on a Chelsea sidewalk on Saturday night. Surveillance video from the neighborhood seemed to show the men unpacking a white plastic bag, leaving it on the sidewalk, then making off with the luggage. The item they left behind was a pressure cooker filled with explosives and wired to blow.

New York Police Chief Robert Boyce said on Monday that the men appeared stunned when they opened the suitcase — but they proceeded to make off with it anyway.

Related: Bombing suspect Ahmad Khan Rahami arrested after shootout in New Jersey

"They look like they were two gentlemen just strolling up and down Seventh Avenue at the time," Boyce said. "Once they picked up the bag, they seemed incredulous. They had actually picked this up off the street and they walked off with it."

The bomb turned out to be a dud. Authorities aren't sure if the removing the bomb from the suitcase somehow disabled it. Another pressure cooker bomb that Rahami allegedly planted in Chelsea injured 29 people and damaged several buildings when it went off.

But the undetonated bomb left behind offered several key pieces of evidence that helped police track down Rahami, including his fingerprint and the cellphone, which was similar to the timing mechanism used in another botched bombing on Saturday in New Jersey.

At first it appeared that the men may have been accomplices, but during a press conference on Monday afternoon following Rahami's arrest in Linden, New Jersey, where he was wounded in a shootout with police, authorities said it appears that the 28-year-old US citizen from Afghanistan acted alone.

William Sweeney Jr., the FBI's assistant director in New York, said there's "no indication that there is a [terrorist] cell operating in the area or the city."

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"Who in this world finds a pressure cooker with a phone and just takes the bag?" a law enforcement source told the local news website DNAInfo, which published the first report about the thieves. Investigators now suspect the thieves had no clue what they were dealing with when they opened the unattended bag.

Coincidentally, another pair of pilferers also helped lead police to a bag of undetonated pipe bombs that were found near a train station in Elizabeth, New Jersey, where Rahami's family lives and owns a restaurant. Authorities said the men saw a backpack sitting on top of a garbage can and opened it, thinking something valuable might be inside. When they saw wires and pipes, the dropped the bag in the street and dialed 911.

Follow Keegan Hamilton on Twitter: @keegan_hamilton