Nearby buildings were evacuated. A 270-foot (82-meter) construction crane — one of two still looming over the multistory building — also was dangerously unstable, fire officials said. The hunt for the missing was suspended at nightfall over safety concerns. A statement from the project contractor said its representatives would work "throughout the night" with emergency officials on a plan to stabilize the building.
"I heard a huge noise and thought it was a plane crashing," said Sue Hurley, a 68-year-old guest at a hostel across the street that shuddered with the force of the collapse. Hurley said she was reminded of news accounts of the 9/11 terrorist attacks.
WWL-TV aired and tweeted a viewer's dramatic video of upper floors falling on top of each other before one side of the building crashed to the street.
Another video on social media showed what looked like a metal structure — part of the building or a piece of construction equipment — tumbling to the ground and people running from the scene as clouds of dust billowed up, obscuring the view like a thick fog.
"I'm not sure what happened, but they told us to get out of here," said Michael Arbeiter, 30, from Munich, Germany, a hostel guest who said he was just getting out of the shower when his room shook. "Thank God it was not another 9/11."
Officials said 18 people were taken to the hospital and several others went to the hospital on their own. They said none of their injuries was believed to be life threatening.
Urban search and rescue teams entered a section of the building Saturday in hopes of finding the two missing people alive, said Fire Chief Tim McConnell. He said authorities believe they know their approximate location based on talks with other survivors of the collapse. One of the two was believed to be in a relatively stable part of the wrecked building; the other, in a less stable area.
Meanwhile, authorities were keeping a wary eye on an unstable construction crane looming over the building.
"There is a very strong possibility of further collapse of this crane right now," McConnell said.
Citadel Builders LLC, the contractor on the project, said more than 100 workers were on site at the time of the collapse. An email from spokesman Brian Trascher said company officials were working with emergency workers on a plan to stabilize the building.
Louisiana Gov. John Bel Edwards visited the site and took part in news briefings soon after the collapse. The Democrat was defending his seat in a primary election Saturday against two major Republican opponents. Edwards was hoping for an outright win to avoid a November runoff.
The new Hard Rock Hotel was under construction at the corner of Rampart Street and Canal Street, a broad boulevard just outside the Quarter that is lined with restaurants hotels and retailers. Canal, which carries six lanes of traffic divided by a wide median where streetcars roll, separates the Quarter from the city's main business district.
As search and rescue efforts unfolded, police stood sentry around a group of people on the Canal Street median who were believed to be loved ones of the missing. A woman nearby said she was trying to find out the status of her brother, a worker at the site. She declined to give her name, wiping tears from her eyes as she walked away.
Removal of the damaged crane and cleanup of massive piles of debris promised to be an enormous undertaking in the days ahead, expected to tie up traffic and commerce. The site is next to two major traffic arteries where major bus and streetcar lines intersect. Among area buildings evacuated was the Saenger Theatre, where traveling companies perform Broadway Shows regularly.
Hard Rock International issued a statement Saturday expressing sympathy for victims and their families. The statement said the company had a licensing agreement with the building's owner, Kailas Companies, and Hard Rock had no involvement in the construction. It identified the contractor on the project as Citadel Builders LLC.
Citadel issued a statement expressing its condolences for the death and injuries but did not comment on a possible cause of the collapse.
Kailas did not respond to messages left seeking comment Saturday night.