Ignacio Maza, whose sister was visiting the Surfside, Fla., condominium when it partially collapsed last week and is now missing, told "America’s Newsroom" that he is "lost without her."

"At this point, we just hope that my sister's remains are found so that we can have a proper funeral service and memorial to honor her and recognize her," Maza, who spoke from New York, said. 

He described his sister, Rosa Saez, a longtime resident of the Surfside community, as "an extraordinary human being."

"She was very compassionate," Maza said of Saez, 70. "She was a wonderful sister, mother, daughter [and] friend." 

"She had a lot of people around her that she cared about," he continued. "She was a very, very special person." 

Maza made the comments shortly after President Biden and his wife Jill arrived in Florida, one week after the collapse of the 12-story Champlain Towers South beachfront condominium in Surfside killed at least 18 people and left 145 missing. 

Biden was scheduled to survey the devastation on Thursday. He met with local officials, including Miami-Dade County Mayor Daniella Levine Cava and Florida Gov. Ron DeSantis, as well as first responders searching for survivors. The president is also expected to meet with the families of those still awaiting word on the status of their loved ones. 

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Since the collapse, hundreds of first responders and search-and-rescue personnel have been searching the rubble for potential signs of life. 

 "At the moment we are hoping that my sister's remains are found," Maza told Fox News’ Trace Gallagher. "I personally don't think that my sister will be found alive at this point. I don't think any human being can last seven full days without water or nourishment."

Before the president arrived at the site, rescue efforts were paused due to concerns about the stability of the section of the building still standing.

Families awaiting word on loved ones have dreaded a transition from a rescue to a recovery mission. On Wednesday, Surfside Mayor Charles Burkett said, "There has been some talk by the families, they’ve asked me if the search is going to stop. Are we going to turn this from a rescue to a recovery?" 

Burkett then pointed to Gov. DeSantis’ comments "where he basically said we're not leaving anybody behind." 

"This is going to go until we pull everybody out of there," Burkett said. "This is our number one effort." 

Some of the families with loved ones still unaccounted for have reportedly expressed frustration by the slow pace of the rescue. 

Rescue crew said they needed to work carefully for the best chance of uncovering survivors, PBS reported on Sunday, adding that one mother, whose 26-year-old daughter was missing and was among relatives who pushed authorities to bring in experts from other countries to help, said the efforts were "not enough." 

"Imagine if your children were in there," she reportedly added. 

The Miami Herald reported on Wednesday that Margarita Castro, a member of the search and rescue team and a Miami-Dade firefighter for nearly two decades, said, "Sometimes all you can do is find a small, quiet corner and just cry for a little while, and let out some of that pressure that you’ve got building up." 

"We each have our moments of strength. We each have our moments of weakness," she continued.

However, Ignacio Maza encouraged anxious families to be strong.

"I think we all have to be patient because the rescue teams are doing the very best they can," Maza told Gallagher on Thursday. 

"These people have had every possible obstacle thrown against them; Thunderstorms, lightning, gas leaks, fires, flooding, collapses … So we all have to understand that this is like a plane crash and it’s devastating and we have to trust the people on the ground to do their best. That's all we can do."

Rosa Saez was born in Cuba and is the fifth of eight children, The Miami Herald reported. The paper said she is a divorced mother of two and a grandmother of six who volunteered often and worked at Florida International University and a Coral Gables travel agency.

"If you live in Miami and leave your house, you probably know her," the newspaper reported. 

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"I’m just glad that we were able to celebrate her 70th birthday a few months ago at a resort in the Dominican Republic with one of my other sisters," Maza said, adding that the trip was especially meaningful given his family "had that moment to honor and recognize her for the very special person that she was."

Fox News’ Greg Norman and The Associated Press contributed to this report.