SURFSIDE, Fla. (NewsNation Now) — Search crews going through the ruins of a Florida condo tower pulled six more bodies from the rubble Wednesday, including two children, bringing the number of confirmed dead to 18. It was the highest one-day toll since the building collapsed almost a week ago into a heap of broken concrete.

The number of residents unaccounted stands at 145.

Miami-Dade Mayor Daniella Levine Cava made the announcement at an evening news conference. She said two the children were ages 10 and 4.

“The loss of our children is too great to bear,” Levine Cava said. “Our community, our nation and the world, we are all mourning with these families who have lost loved ones.”

Gov. Ron DeSantis, in a one-on-one interview with NewsNationNow.com, said meeting with victims’ families has been devastating. “When you’re actually sitting down face-to-face and you see just the inconsolable grief of somebody whose world has been shattered,” he said.

DeSantis offered support for a grand jury to probe the building collapse.

Authorities said their efforts were still a search-and-rescue operation, but no one has been found alive from the mounds of pulverized concrete, splintered lumber and twisted metal since hours after the collapse on Thursday.

Earlier in the day Wednesday, crews searching for survivors built a ramp that should allow the use of heavier equipment, potentially accelerating the removal of concrete that “could lead to incredibly good news events,” the state fire marshal said Wednesday.

Rescuers have been working to peel back layers of concrete on the pancaked building without disturbing the unstable pile of debris.

Miami-Dade Assistant Fire Chief Raide Jadallah told family members of those missing Wednesday that a ramp built onto the pile overnight allowed rescuers to use a crane on sections that were not previously accessible. He said that improves the chances of finding new pockets of space in the urgent search for survivors.

“We hope to start seeing some significant improvement in regards to the possibility of (finding) any voids that we cannot see,” Jadallah said.

Miami-Dade Fire Rescue Chief Alan Cominsky said earlier this week that search personnel faced a daunting task while working in 12-hour shifts in the heat and humidity, hampered by intermittent showers and thunderstorms.

Crews are now keeping an eye on two disorganized storm systems in the Atlantic Ocean. The National Hurricane Center said the storms have a chance of becoming tropical systems in the coming days, but it is unclear at this point whether they would pose a threat to the U.S.

DeSantis said some of the resources in Surfside might have to be removed in case the storms hit any part of Florida. “’Tis the season and you’ve got to be ready,” he said.

The possibility of severe weather prompted state officials to ask the federal government for an additional search and rescue team. Kevin Guthrie of the Florida Division of Emergency Management said the new team, which would likely come from Virginia, would be on hand if severe weather hits, allowing crews that have been working at the site for days to rotate out.

Investigators have not concluded what caused nearly half of the 40-year-old Champlain Towers South condo to crumple as residents slept in the early hours of last Thursday.

“I understand the odds against us, however myself and my family are not ready to give up,” Rachel Spiegel said as she waits for word about her mother, Judy. “We’re not ready. I’m pulling my strength from the love I have from my mom, the love my kids have for my mom, and my poor dad – the best husband in the world.”

But a 2018 engineer’s report on the 12-floor, 136-unit complex, prepared ahead of a building safety recertification process, found structural deficiencies that are now the focus of inquiries.

As recently as April, the condo association’s president warned residents in a letter that severe concrete damage identified by the engineer around the base of the building had since grown “significantly worse.”

President Joe Biden and his wife, Jill Biden, planned to pay a visit on Thursday to the scene of the tragedy in the oceanfront town of Surfside, adjacent to Miami Beach, the White House said.

The town of Surfside has a population of just over 5,000. The area is a mix of new and old apartments, houses, condominiums and hotels, with restaurants and stores serving an international combination of residents and tourists. The community provides a stark contrast from bustle and glitz of South Beach with a slower paced neighborhood feel.