New Orleans mayor vows 'relentless' investigation in deadly Hard Rock Hotel collapse Authorities said building remains too unstable to search.

Crews were feverishly working on Sunday to stabilize the Hard Rock Hotel in downtown New Orleans a day after the building partially collapsed, killing two construction workers, leaving a third trapped in the rubble and injuring 30 others, officials said.

One body has been recovered from the scene, according to New Orleans mayor LaToya Cantrell.

New Orleans Fire Chief Tim McConnell said at a news conference near the disaster site on Sunday that search-and-rescue crews were poised to reenter the building.

"Search and rescue continues to be our top priority at this time," McConnell said.

He said the search of the building that had been under construction was halted overnight after conditions were deemed too dangerous to allow first responders to enter.

McConnell said a large crane was also damaged in the collapse and remained in a precarious position. He said a massive crane weighing 110 tons was trucked into the city overnight from Baton Rouge and will be used to help stabilize the building once it's assembled.

Hazardous conditions, according to the chief, prevented search teams from recovering the bodies of the two construction workers killed when the upper floors of the building suddenly gave way and pancaked on one another. He said the identities of the dead construction workers and the one who remains missing have yet to be confirmed.

"This is not something you take lightly," McConnell said of the search efforts. "Safety is the No. 1 thing. The last thing you want to do as you're trying to rescue someone is lose someone else."

Dr. Emily Nichols, director of Emergency Medical Services in New Orleans, said of the 30 people treated for injuries, only one remained hospitalized on Sunday.

Mayor Cantrell said she visited the injured worker late Saturday night at University Medical Center New Orleans. She said the worker, who is in stable condition, suffered a fractured femur and underwent surgery.

"He is in the best of spirits that he can be in," Cantrell said. "He told me that it could have been worse. He said it happened very fast. He heard noise, looked around and moved very, very quickly."

Cantrell said the investigation into the collapse will get underway once everyone believed to have been inside the building at the time of the collapse is accounted for.

"After search and rescue, it will shift into a full-investigative mode and we will be relentless in those efforts moving forward," Cantrell said.

She identified Citadel Builders, based in Metairie, Louisiana, as the general contractor on the Hard Rock Hotel construction project. The 18-story, 350-room hotel near the city's French Quarter and Theater District was scheduled to open in 2020.

Brian Trascher, a spokesman for Citadel Builders, told ABC News on Sunday that the company is working closely with the city to stabilize the building.

"Our team is pretty much part of the incident command. We're working nonstop. There's no fusing, no arguing, no pointing fingers right now," Trascher said.

Trasher said the cause of the collapse remains under investigation.

According to preliminary information, all permits had been obtained to complete the building and that everything was "up to code," Cantrell said.

Trascher said the big problem on Sunday afternoon was how to secure the damaged crane that was listing from the side of the collapsed building. A top engineer for the company who operates the crane was flying in from Germany to assist local officials, he added.

The collapse happened around 9:12 a.m. local time at Canal and North Rampart Streets, McConnell said.

Trasher said more than 110 construction workers were on site when the collapse happened.

In a statement to ABC News, Citadel Builders said that it "remains committed to the safety and well being of all first responders and SAR teams working in and around our construction site in New Orleans. While the process may not always move at the desired pace, rest assured that our team continues to work closely with Mayor Cantrell and Chief McConnell's personnel on the scene."

"Multiple internal and external investigations are in progress, but we are still in the infancy stages as we have not yet had access to the building. This situation is being handled much like a plane crash, in that rescue/recovery are the primary functions, followed by the search for physical and technical indicators that may provide clues to the cause," the statement continued.

Citadel Builders has flown in the chief engineer for Morrow Cranes, the crane owner, as well as the head engineer of the manufacturer from Munich, Germany, to aid in the recovery effort, according to the statement.

Officials said it appeared the collapse initially affected the sixth to eighth floors before damage spread throughout a large portion of the building.

Dramatic video of the incident showed parts of the building crashing into the street as debris billowed into the air.

Cantrell said that 10 surrounding buildings, including condominiums, were evacuated and that electricity and gas to those buildings remained turned off on Sunday. Nearby streets were closed to vehicles, according to NOLA Ready, the city's emergency preparedness center.

The mayor said debris from the collapse caused extensive damage to the roof of the historic Saenger Theater across the street, forcing the remaining performances of the musical "Wicked" to be canceled.

Hard Rock International said in a statement the company had "no involvement in the construction of the project" but extended its "deepest sympathies to victims of this tragic accident and to their loved ones and friends."

ABC News' Ahmad Hemingway, Devin Vilacis and Matt Foster contributed to this report.