The number of people killed from last week's partial collapse of a Florida condominium building rose to 10 on Monday as search and rescue squads found another body in the sprawling debris field.

Miami-Dade County Mayor Daniella Levine Cava told reporters that 151 people remain missing with 135 others accounted for following Thursday's early-morning collapse of the Champlain Towers South in Surfside, Florida.

"The search and rescue operation continues," Cava said. "There’s going to be a thorough and full investigation of what led to this tragic event."

No one has been pulled from the rubble alive since the search began on Thursday.

Over 80 rescuers are on site sifting through concrete and metal that spilled below ground in to a parking garage. Heavy equipment, including a crane, has been brought on site to help remove larger pieces of debris.

Families of the missing have been bused to the area to observe the rescue operation.

Miami-Dade Fire Rescue Chief Alan Cominsky said his teams are struggling with a "very challenging, very difficult situation" as they sift through rubble that continues to shift four days after the initial collapse, requiring meticulous work from personnel.

"We're talking about pulverized concrete. We're talking about steel," assistant fire chief Raide Jadallah said. "Every time there's an action there's a reaction."

A rescuer on Sunday tumbled 25 feet (and 7.6 meters) down the debris mound as family members who were present at the site looked on, Jadallah said.

"It's not an issue of we can just attach a couple cords to a concrete boulder and lift it and call it a day. We're digging through again rubbles of concrete the size of basketballs, the size of baseballs, and then and only then in combination with the safety of the personnel, and of course, considering the victims themselves, it's going to take time," he added./aa