Security posts known as barricades were not in place before a suspect drove a truck into a crowd of people in New Orleans' French Quarter early on New Year's Day, killing 14 people and wounding at least 35.
Louisiana officials said street barriers were down and undergoing renovations before the city hosts NFL football on February 9.
The short, sturdy bollards – made of concrete, metal or other materials – are intended to prevent cars from entering pedestrian zones.
On Thursday, Christopher Raya, deputy assistant director of the FBI, described the attack as an act of terrorism.
During the early morning hours of New Year's Day, a police car was parked at an intersection blocking access to Bourbon Street in the French Quarter, where the attack occurred, but the suspect drove around the car and onto the sidewalk, police said.
Police named Shams al-Din Jabbar, 42, a Texas resident and US Army veteran, as the suspect. He died in the attack.
New Orleans Police Chief Anne Kirkpatrick said Wednesday that police were “aware of the barrier position” and had taken steps to “reinforce those targeted areas.”
She added: “We already had a plan, but the terrorist thwarted it.”
Ms Kirkpatrick said the city plans to take a number of steps to beef up security at the Sugar Bowl football game, which was moved from Wednesday to Thursday afternoon due to the attack.
Bourbon Street will reopen Thursday shortly before the game.
“We have reconsolidated the area,” Louisiana Governor Jeff Landry said Thursday.
- Follow live updates on the attack here
The city of New Orleans began placing barriers on Bourbon Street more than a decade ago, Mayor LaToya Cantrell said Wednesday.
But she added that the poles began malfunctioning 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 Caesars Superdome, near the site of the attack.
At the news conference, Ms. Kirkpatrick defended other security measures the city has taken.
“We had a car there, we had barricades there, we had officers there, and they're still walking around,” she said.
A number of cities in the United States and around the world have installed barriers to prevent attacks.
New York City placed security measures along the bike path in Hudson River Park after a man drove a rental pickup truck into cyclists and runners along the path, killing eight people in 2017.
Javed Ali, a University of Michigan professor and counterterrorism expert, said it is very difficult to say with certainty whether New Orleans' barriers put in place would prevent such an incident from occurring.
“He had a Ford 150 pickup truck. You could launch this thing at 50 or 60 miles per hour, and who knows, even with the barriers in place, would the car have hit it anyway?” He said.
“It must have been a lot of luck,” Mr. Ali added. “This is unfortunately what happens in these types of attacks.”
A 2017 report commissioned by the City of New Orleans found that the French Quarter was “a risk area and target for terrorism that the FBI has identified as a concern that the city must address.”
The report noted that the neighborhood “was often crowded with pedestrians and represented an area where mass casualties could occur.”
