(CNN) Crews in New Orleans are trying to rescue two workers trapped in the wreckage of a Hard Rock Hotel under construction that collapsed on Saturday.

"We believe we know where they are but we have no visibility," Tim McConnell, New Orleans Fire Department Superintendent, told reporters. "We assume they are alive."

Search and rescue teams are using dogs and drones to make contact with the workers but one crane needs to be secured before the teams can enter the building, a statement from Citadel Builders, the general contractor over the project, said.

"Citadel representatives remain engaged and will be working with the City and engineering experts throughout the night and until a solution can be implemented," Citadel Builders spokesman Brian Trascher said in the statement.

More than 100 workers were on site at the time of the collapse, the statement said.

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