Security posts, known as bollards, were not in place before a suspect drove a truck into a crowd in New Orleans' French Quarter early on New Year's Day, killing 14 and injuring at least 35.
Louisiana officials said the street barriers were malfunctioning and were being repaired before the city hosted the NFL Super Bowl on Feb. 9.
Short and strong posts – made of concrete, metal or other materials – are designed to block the entry of cars into pedestrian areas.
Christopher Raya, deputy assistant director of the FBI, on Thursday called the attack an act of terrorism.
In the early morning hours of New Year's Day, a police car was parked at an intersection to block access to Bourbon Street in the French Quarter, where the attack took place, but the suspect drove around the car and onto the sidewalk, police said.
Police named Shamsud-Deen Jabbar, a 42-year-old Texas resident and U.S. Army veteran, as a suspect. He died in the attack.
New Orleans Police Chief Anne Kirkpatrick said Wednesday that police were “aware of the bollard situation” and had taken steps to “harden those targeted areas.”
“We did have a plan, but the terrorist defeated it,” she said.
Ms. Kirkpatrick said the city planned to take a number of steps to increase security for the Sugar Bowl, which was moved from Wednesday to Thursday afternoon because of the attack.
Bourbon Street will reopen Thursday shortly before the game.
“We supported the area,” Louisiana Gov. Jeff Landry said Thursday.
- Follow live updates on the attack here
New Orleans began putting bollards on Bourbon Street more than a decade ago, Mayor LaToya Cantrell said Wednesday.
But, she added, the poles began to malfunction due to blockages from Mardi Gras beads, prompting officials to try to replace them before the Super Bowl, which is scheduled to be held at the Caesars Superdome, near the site of the attack.
At the press conference, Ms. Kirkpatrick defended the other security measures the city has in place.
“We had a car there, we had barriers there, we had officers there and they were still moving,” she said.
A number of cities in the US and around the world have installed bollards to prevent attacks.
New York introduced security measures along the Hudson River Park bike path after in 2017 a man plowed a rented pickup truck into bicyclists and joggers on the sidewalk, killing eight people.
It's too hard to say for sure whether the bollards in New Orleans would have prevented a similar incident, said University of Michigan professor and counterterrorism expert Javed Ali.
“He had a Ford 150 pickup. You're shooting that thing at 50, 60 miles an hour, and who knows, even with the pins in place, would the car just — through physics — still crash through them?” he said.
“It must have been a lot of luck,” added Mr Ali. “Unfortunately, this is what happens in these types of attacks.”
A 2017 report commissioned by the city of New Orleans found the French Quarter to be “a risk and target area for terrorism that the FBI has identified as a problem the city needs to address.”
The report notes that the neighborhood is “often densely packed with pedestrians and represents an area where a mass casualty incident could occur.”