The hotel's design features an 11-story tower set back atop a seven-story podium. The structural failure appeared to originate in the upper floors of the setback section of the hotel. Amateur videos of the collapse show portions of the top concrete floors collapsing, sending debris into the streets and damaging a tower crane at the site. 

Structural engineering experts who have reviewed video of the collapse offered possible explanations for the failure to ENR, none could make firm conclusions about the ultimate cause.

As of Oct. 15, officials had not reached any conclusion about possible causes. A swimming pool had been lifted to the 14th floor hours before the collapse, but according to Citadel Builders, the pool was placed on the opposite side of the building from where the collapse would later occur. A New Orleans Fire Dept. spokesperson said that a drain has since been installed in the pool to prevent rainwater from collecting and adding to the load on the structure.

General contractor Citadel Builders told ENR that it had roughly 130 workers on the site at the time, although many were on break when the accident occured.  Citadel Builders is now working with emergency workers to stabilize the building. 

Structural engineer Heaslip Engineering, and sheetrock and metal framing subcontractor King Cos. did not respond to inquires from ENR by press time. The project's architect, HBSA II, declined to comment on the incident when contacted by ENR. The project is owned by developer Kailas Companies. Hard Rock International, owner of the Hard Rock brand, said in a press statement that it had licensed the brand to Kailas Companies and was not involved in the construction of the hotel.

The cause of the collapse has not yet been determined, according to officials. Multiple eyewitnesses reported that the collapse began on the upper floor slabs of the unfinished hotel. Two Liebherr tower cranes were in place at the site, and it is unclear if they were involved in the collapse. One of the cranes was visibly damaged during the collapse, posing a hazard to rescuers and investigators responding to the site [Further details on status of cranes below].

“Search and rescue continues to remain our top priority at this time,” said New Orleans Mayor LaToya Cantrell in a public briefing on Sunday morning. She added that road closures in the busy downtown of the city would continue while crews worked to stabilize the building. “This is going to be a long process,” she said. 

Damaged Tower Cranes Pose Problem for Stabilizing Building Site

OSHA investigators were on site Sunday, but the unstable structure and the damaged tower crane limited crews abilities to traverse the site. Support cranes were brought in Sunday to assist in dismantling the damaged cranes. Concerns over the instability of the cranes and the remaining structure have slowed the investigation and cleanup. 

In statement to ENR on Oct. 14, Citadel Buildings said "the structure, and particularly the rear tower crane attached, continue to cause safety obstacles to the search and rescue/recovery efforts. We have flown in the chief engineer for [crane owner] Morrow Cranes, as well as the head engineer of the manufacturer [Liebherr] from Munich, Germany. We want the best possible intelligence as to the strengths and weaknesses of the damaged crane."

According to Citadel Builders, backup cranes have arrived on the scene and are being assembled to assist in dismantling the damaged tower cranes. "Once we are confident that the tower crane can be secured as safely as possible, authorities will then be able to determine when and how to proceed with search and rescue/recover," the company said in the statement. The company also announced it has retained Thornton Tomasetti to assist in the assessment and stabilization of the building site.

Trey Caruso, a spokesman for the City of New Orleans told ENR on Monday afternoon that while support cranes were set up to help in dismantling the two tower cranes, they had to abandon those initial efforts due to the cranes' instability. Experts from Morrow Crane and Liebherr concluded in their initial onsite assessment that the tower crane located further from the collapse site is not as stable as they originally thought, meaning both cranes are now being treated as unstable. “We’ve got cameras and lasers monitoring the position of the cranes now,” Caruso told ENR.

“We still have a ton of engineers here and more arriving to figure out exactly how we are going to mitigate the situation,” says New Orleans Fire Department Chief Timothy McConnell. 

The team responding to the collapse had been evaluating several different options for securing the cranes and had brought in support cranes to aid in the effort. But those efforts were halted on Monday after engineers determined those efforts could put the two cranes at risk of collapse, an assessment further confirmed after consulting with the cranes' manufacturer. “When the engineers got here and looked at that plan, they said absolutely not,” McConnell says.

Officials were aware that one of the two cranes was damaged but learned on Monday that the crane closest to Canal Street was just as much at risk and not as stable as originally thought.

“They’re amazed that either crane is standing,” McConnell says.

Inclement Weather Hampers Search and Rescue Operation

Wind and rain posed a concern Monday evening as both cranes remained precariously positioned.

“Any water put on the building could cause more possibility of damage,” McConnell says.

City officials have received reports that debris dangling from the building continues to fall off. As a precaution, the city expanded the evacuation zone surrounding the building early Monday afternoon.

Search and rescue teams, along with rescue dogs, spent Monday looking for the construction worker who remains unaccounted for. No demolition will take place until the rescue mission is complete, McConnell says.

“We are still very much in rescue mode,” he says.

By Jeff Rubenstone, with reporting from Autumn Cafiero Giusti in New Orleans

The text of this article has been updated to reflect new information.