The FBI and Department of Homeland Security on Thursday issued a joint intelligence bulletin warning the nation’s 18,000 law-enforcement agencies about potential copycats seeking to emulate this week’s devastating ramming and shooting attack in New Orleans, ABC News has learned.

The bulletin was sent out of an abundance of caution to sensitize law enforcement around the country to be on the lookout for any activity pointing to the use of vehicles as a method to inflict mass casualties, sources told ABC News.

The bulletin notes that ISIS — to which New Orleans suspect Shamsud-Din Jabbar pledged allegiance before the New Orleans attack, according to FBI Deputy Assistant Director Christopher Raia — has been promoting the use of vehicles as a terrorism weapon since around 2014.

Sources told ABC News that ISIS has ramped up calls for its supporters to launch low-tech, mass casualty ramming attacks in recent months, especially since the most recent Israel-Hamas conflict began in October 2023.

The bulletin offered law enforcement agencies tips on danger signs of upcoming attacks to look out for, including the use of pre-operational surveillance and fraudulent identity documents or credit to rent vehicles.

The bulletin stated that Jabbar was inspired by ISIS but that there remains no evidence of any co-conspirators. A senior law-enforcement official told ABC News that there is so far no sign of ISIS claiming responsibility for the New Orleans attack.

The ongoing investigation into the New Year’s Day attack on Bourbon Street saw bomb-making materials recovered by FBI agents and local law enforcement at a residence linked to the suspect in Houston, Texas, on Thursday, sources confirmed to ABC News.

The items found were also referred to as “precursor chemicals” by agents in the field, sources said. They were discovered during the execution of a search warrant at Jabbar’s last known residence in the small community of Greenspoint, in north Houston.

Authorities no longer believe there are any other suspects involved in the New Year’s truck attack that killed 14 people and injured 35 others, the FBI said Thursday.

Sixteen people remain hospitalized at University Medical Center New Orleans, including eight in intensive care. The death toll is not expected to rise beyond 14 people, Dr. Jeffrey Elder of the University Medical Center New Orleans told ABC News Live on Thursday.

After investigators reviewed all surveillance videos, it appears that Jabbar — a 42-year-old Army veteran and U.S.-born citizen from Texas, who also died in the attack — placed explosive devices in the area himself and then changed clothes, multiple law enforcement sources told ABC News.

The FBI is still investigating whether there were individuals Jabbar spoke to or exchanged messages with prior to the early morning Wednesday attack, but no one was in the vicinity to help him do anything, the sources said.

“Federal law enforcement and the intelligence community are actively investigating any foreign or domestic contacts in connection that could possibly be relevant to the attack,” President Joe Biden said Thursday.

The FBI’s Raia called the attack a premeditated “act of terrorism” but said there was no additional threat to the public.

The FBI released new surveillance images of Jabbar in New Orleans a little more than an hour before the attack took place, showing the suspect walking along Dauphine Street near Governor Nicholls Street shortly after 2 a.m., wearing a light brown long coat, jeans and brown dress shoes.

The FBI also released a photo of one of the coolers containing an explosive device that authorities said Jabbar placed near the intersection of Bourbon and Orleans Street.

Surveillance footage showed Jabbar placing two improvised explosive devices in coolers in the Bourbon Street area, Raia said. He had a remote detonator in the truck to set off the two devices, Biden said.

“Those are the only two devices that we’ve been able to recover that were functional — both devices were rendered safe on scene,” he said.

Jabbar drove from Houston to New Orleans on Tuesday evening and posted several videos online “proclaiming his support for ISIS,” and mentioning he joined ISIS before this summer, Raia said.

Jabbar was “hell-bent” on killing as many people as possible, driving a pickup truck onto the sidewalk around a parked police car serving as a barricade to plow into pedestrians, officials said.

The suspect mowed down dozens of people over a three-block stretch on the world-famous thoroughfare while firing into the crowd, police said.

Jabbar then exited the damaged vehicle armed with an assault rifle and opened fire on police officers, law enforcement said. He was also armed with a handgun, sources told ABC News.

Officers returned fire, killing Jabbar. At least two officers were injured, one by gunfire and the other when the officer was pinned by the truck, authorities said.

New Orleans Police Superintendent Anne Kirkpatrick said security bollards were not working at the time because they were in the process of being replaced for next month’s Super Bowl.

Law enforcement cleared and reopened Bourbon Street on Thursday as the investigation continued. New Orleans Mayor LaToya Cantrell said authorities had the “confidence” to reopen the area to the public ahead of the Sugar Bowl Thursday afternoon, which was initially scheduled for Wednesday but postponed in the wake of the attack.

“I want to reassure the public that the city of New Orleans is not only ready for game day today, but we’re ready to continue to host large-scale events in our city,” she said. “Our hearts and prayers continue to go out to the victims’ families,” Cantrell added.

Louisiana Gov. Jeff Landry on Thursday compared the ongoing investigation to a jigsaw puzzle.

Over 400 tips have been submitted and investigators are combing through Jabbar’s laptops and phones, Raia said. More than 1,000 law enforcement officers have been “pouring over countless amounts of data, of videos, of surveillances, interviews, tracking down every possible lead,” Landry said.

Authorities have conducted search warrants in New Orleans and outside of Louisiana, the FBI’s New Orleans field office said.

There is no apparent direct connection between the New Orleans attack and Wednesday’s Tesla Cybertruck explosion outside the Trump International Hotel Las Vegas, which is also being investigated as a possible act of terror, Raia from the FBI said Thursday.

Biden said Thursday that investigators “have not found any evidence of such a connection thus far — I’ve directed them to keep looking.”

The Las Vegas driver was killed and seven bystanders suffered minor injuries, authorities said. The motive behind the incident remains under investigation, but investigators told ABC News they believe it was “intentional.”

The Cybertruck was rented via the Turo app, as was the truck used in the New Orleans attack, sources told ABC News.

The Cybertruck driver had an Army special operations background but there is no evidence suggesting he and the New Orleans suspect knew each other, according to officials.