Search and rescue crews were back Thursday night to sifting through the rubble at the site of the Surfside, Florida, condo building collapse, still hoping to find any signs of life, while officials said the remaining section of the tower that didn’t fall will likely have to be demolished.

Only in portions of the site that are safe have search and rescue efforts resumed, Miami-Dade County Mayor Daniella Levine Cava said Thursday.

Sections of the debris have been labeled into a grid. Rescuers are only able to resume searching in three of the nine portions of the grid, said Alan Cominsky, Miami-Dade County fire chief.

The rest of the standing building will likely be taken down, Levine Cava said, but the decision needs to be made methodically to evaluate all possible impacts to the pile of debris and to the continued search and rescue efforts.

Scott Nacheman, a structures specialist with the Federal Emergency Management Agency, said there is not yet a definitive timeline for when the remaining building will be torn down, but a decision could take weeks, at best. If the building were demolished, Nacheman said, it would initially slow rescue efforts.

Local officials paused the search in the early hours of Thursday morning after structural engineers expressed concerns about movement of a portion of the Champlain Towers South complex that did not collapse when other sections fell one week ago.

Teams of state experts are studying the problem: widening cracks and up to a foot of movement in a large column.

No survivors have been found since the initial hours after the disaster.

Miami-Dade police identified a 17th victim as 80-year-old Magaly Elena Delgado Thursday. Rescuers recovered her body Wednesday.

The official count is 18 dead and 145 people unaccounted for.

In an attempt to avoid a similar tragedy, Surfside is requesting property owners begin assessing their buildings 30 years and older and over three stories tall before the typical 40-year recertification.

Property owners with buildings that fit the description and those with buildings on the east side of Collins Avenue near the ocean should hire a licensed geotechnical engineer to analyze “the foundation and subsurface soils,” said a letter from the Surfside Building Department.

In remarks to the country, Biden stressed the importance of continuing the rescue mission as soon as experts clear the way. And he says it’s critical for investigations to find out why the 40-year-old tower fell, whether adjacent towers are safe, and how to prevent the same kind of collapse from happening elsewhere.

“We’re committed not only to recover but to restore safety across the board,” he said.

Biden met privately with affected family members for over three hours, then spoke about their ordeal.

“The whole nation is mourning with these families,” he said. “They’re going through hell, those who survived the collapse as well as those missing loved ones.”

The president said he made sure to speak personally with each person in the room, and listen to their “heart-wrenching questions: Will I be able to recover the body of my son or daughter, my husband, my cousin, my mom and dad?”

Some of his comments from the private meeting appeared on social media.

“I just wish there was something I could do to ease the pain,” he said in a video posted on Instagram by Jacqueline Patoka, a woman who was close to a couple and their daughter who are still missing.

Biden described his own grief from losing family members.

“The people you may have lost — they’re gonna be with you your whole life,” he told the families. “A part of your soul, a part of who you are.”

“But I promise you: I still believe in prayer,” he said. “You’re in my prayers.”

Before leaving to return to Washington, Biden and first lady Jill Biden stopped by a memorial near the disaster site. She laid a flower bouquet, and Biden, a devout Catholic, made the sign of the cross, bowed his head, and a few seconds later, made another sign of the cross.

The president began the visit by receiving a briefing from DeSantis, Levine Cava and other officials at the St. Regis Bal Harbour Resort. Florida Sens. Marco Rubio and Rick Scott, and U.S. Rep. Debbie Wasserman Schultz, whose district includes Surfside, also attended the session with the president.

“I want to pick up 100% of the cost from the county and the state over the first 30 days,” Biden said in his opening remarks. “I think I’m quite sure I can do that.”

The president said federal support is critical because “there’s going to be a lot of pain, and anxiety and suffering, and the need for psychological help in the days and months that follow, and so we’re not going anywhere, for real.”

“Mr. President, we cannot thank you enough for being here with us, for showing your extraordinary support from day one,” Levine Cava said. “We are going to be examining every inch of this catastrophe.”

DeSantis also thanked Biden for the federal government’s assistance, noting that it’s been free of any bureaucratic obstacles.

“What we just need now is a little bit of luck, a little bit of prayer,” the governor said. “We would like to see some miracles happen.”

Just before noon, the Bidens met with around 50 uniformed first responders in a hotel ballroom.

“What you’re doing now is just hard as hell to deal with, even psychologically, to deal with,” Biden told a group of first responders gathered at the resort, not far from the collapsed condo tower. “I just want to say thank you. Thank you, thank you, thank you.”

“Until we need you, no one fully appreciates what you do,” Biden added. “But I promise you — we know. We know. What you’re doing here is incredible, having to deal with the uncertainty, and worrying about the families.”

Crews spotted several expansions in cracks they had been monitoring. They also observed 6 to 12 inches of movement in a large column hanging from the structure “that could fall and cause damage to support columns” in an underground parking garage, Cominsky said.

Workers also noticed movement in the debris pile and slight movement in some concrete floor slabs “that could cause additional failure of the building,” he said.

Critical points around the site have been monitored with sensors since the rescue operation began, Nacheman said. In an interview with The Associated Press, he said there were alarming indications of movement Wednesday night at three locations.

“What was of specific concern was that over the last six days we had not seen that type of significant movement, or in some locations any movement in those elements of the structure,” Nacheman said Thursday during a briefing for family members.

Heavy equipment in the rubble pile caused vibrations, according to Nacheman. Rain has also been entering exposed parts of the building, saturating items and adding weight to the floors, according to the AP report.

On Thursday, DeSantis said emergency managers were watching Tropical Storm Elsa, which has formed in the Atlantic. All of South Florida is in its current forecast path, though no storm impacts are expected through Saturday.

Before the unexpected pause on the search efforts, the work had accelerated Wednesday with the addition of a new ramp and a crane to haul away massive pieces of concrete — offering a glimmer of hope to families of missing residents.

Mindful of the fears gripping relatives of the suspected victims, authorities had vowed to continue the search around the clock.

“Obviously we believe that continuing searching is something that’s very, very important,” the governor said.

The Surfside emergency has received the state’s largest disaster response for any nonhurricane event. More than 500 workers from across the state and from Israel and Mexico had been working at the scene.

Authorities say the public can help too. Miami-Dade police are asking for anyone who may have witnessed the collapse or has photos or videos to contact a tip line at (305) 428-4417 between the hours of 8 a.m. and 1 a.m. Eastern time.

Across the street from the wreckage, people continued to come pray and pay respects at a memorial near St. Joseph’s Catholic Church. Several members of the congregation are either missing or dead, including the Guara family with the two young sisters Lucia and Emma, according to WPLG-TV.

Manny Moreno, 39, of Wynwood, came with his 8-year-old Chihuahua mix, Brownie. Kneeling down in his Birkenstocks and cut off jean shorts, Moreno quietly lit more than a dozen candles one by one.

Moreno, who served in the military and was “traumatized” after 9/11, said he got emotional when he heard about the building collapse and wanted to show his support during such a sad time.

“It’s a good thing when people come together,” Moreno said.