(CNN)For a sixth day, search and rescue crews made their way meticulously through piles of rubble after the condo collapse in Surfside, Florida, hoping to find more survivors.
As of Tuesday evening, at least 12 people are dead and 149 people are unaccounted, officials said. Miami-Dade Fire Rescue crews searching the pile of rubble on Friday. “We’re moving debris piece by piece and searching through,” Miami-Dade Fire Chief Alan Cominsky said Tuesday, describing what he called a “tedious process.” Crews from all over the state have been helping out. The US Federal Emergency Management Agency (FEMA) has sent assistance, and crews from Israel and Mexico are also helping.Here are some of the challenges the crews are facing.Read MoreDebris is fallingThe pieces of concrete the crews are dealing with are the size of basketballs and baseballs, Raide Jadallah, the assistant fire chief of operations for Miami-Dade Fire Rescue, said Monday. Miami-Dade County Mayor Daniella Levine Cava said Friday that debris is falling on crews at the site as they do their work.”We have structural engineers on site to assure that they will not be injured, but they are proceeding because they are so motivated,” Levine Cava added.Debris is also shiftingOvernight into Tuesday, debris fell from portions of the building that remain standing, Surfside Mayor Charles Burkett said.And workers were steering clear of a “45-foot area next to the building” because of concerns about overhanging debris from the standing portion, Cominsky said.The west side had to cordoned off “because it was becoming excessively dangerous to work there,” Burkett said. This is what we know about the dead and unaccounted for in the Miami condo collapseThe pile of rubble shifts as the crews work, officials said.”The situation at hand is we’re not lifting floor by floor,” Jadallah said. “We’re talking about concrete. We’re talking about steel. Every time there’s an action, there’s a reaction.”He said on Sunday as crews were looking through the rubble, a rescuer fell 25 feet down the pile of collapsed building.”That’s a perfect example of the situation we’re dealing with. This was, again, witnessed by the family members themselves at the site,” he said. “It’s not an issue of we can just attach a couple of cords to a concrete Boulder and lift it and call it a day.”There’s a lot of rubble to moveThe building was 12 stories high. The crews have so far moved about 3 million pounds of concrete, Kominsky said Tuesday. “That’s over 850 cubic feet,” he said. While crews were looking for empty spaces in the rubble where survivors might be by digging in from the bottom, heavy machinery has been lifting pieces from the top. But people who were sleeping in their bedrooms when the building fell in “are under four or five meters (13 to 16 feet) of concrete,” Col. Golan Vach, the commander of the Israeli National Rescue Unit that’s assisting in the search, told CNN’s Wolf Blitzer Tuesday. “So this is what they’re doing right now, penetrating the concrete,” Vach said. Vach said that of all the places he has done similar work — Turkey, Haiti, Albania and Mexico, for example — this site is the most difficult because of the way the building pancaked in on itself.Jadallah emphasized that the process is “going to take time.””It’s not going to happen overnight,” Jadallah said. “It’s a 12-story building. It’s going to take some time.”A few fires broke out at the siteWhen a few fires broke out at the site over the weekend, crews had to work to get that and the smoke under control.Levine Cava said Saturday that progress had been made with the fire and smoke that was hampering the search effort. Wind, rain can make the rescue more dangerousIt’s the rainy season in Florida, and the wind and rain only made a dangerous situation even more so, officials pointed out. Some work had to stop at times because of lightning. On Sunday, Burkett said rescuers luck had “seemed to turn” as far as fires and weather were concerned.Now, he said, “we just need a few more miracles each day.”