Rescuers search the rubble for a sixth day as families await answers about their loved ones and what caused the collapse.

(CNN) – As rescuers begin their sixth day searching the rubble of a deadly landslide of a condo in Florida, the families of the disappeared are desperately searching for information about their loved ones and investigators are on the scene trying to find out the cause.

At least 11 people have died in the collapse of the Champlain Towers and 150 are still missing after the tragedy. More than 136 people have been counted, according to Miami-Dade Mayor Daniella Levine Cava. The deceased victims are between 26 and 82 years old.

“We are not losing hope. We’re there every day, ”Rachel Spiegel, whose mother Judy Spiegel is missing, told CNN’s Don Lemon on Monday. “I am concerned that five, almost six days have passed and we have found 11 people and there are still 150 missing,” he added.

A six-person team of federal officials from the National Institute of Standards and Technology (NIST), consisting of scientists, structural engineers, and a geotechnical engineer, is conducting a preliminary investigation of the collapsed building’s materials, history, and building codes. construction applicable at the time the condo was built, the terrain surrounding the building and many other factors, according to an agency official.

As researchers converge on the scene, questions continue to arise about the building’s structural integrity. A 2018 report from an engineering company showed severe structural damage to the concrete slab below the pool deck and “cracks and chips” in the parking lot.

Chipping or chipping is a term used to describe areas of concrete that have cracked or crumbled.

Residents of the building had also raised concerns about tremors during the construction of a nearby building in 2019, according to documents obtained by CNN and interviews with relatives of those missing in the collapse.

Donna DiMaggio Berger, an attorney for the condo’s board, told CNN’s Chris Cuomo on Monday that she didn’t think the building was in disrepair before its collapse.

“We have months and years to investigate what happened, and we will. The board is already in the process of hiring an engineer to also try to find out what happened, and they will assess who is responsible.

Condo owners faced appraisals of $ 15 million in building repairs, with payments scheduled to begin July 1.

The association approved the assessment in April to complete the repairs required under the county’s 40-year recertification process, according to documents obtained by CNN.

The investigation will take months

Although there are no clear answers on the cause, the first indications point to some failure in the lower sections of the 13-story building, perhaps in its foundations, columns or underground parking, according to experts.

Forensic engineers will need to examine the ground-floor columns in their investigation, Sinisa Kolar, a Miami-based engineering executive, told CNN.

He explained that the concrete samples should be tested to examine the condition and then those samples should be checked against structural drawings.

“The key element of this investigation, in my opinion, is in those rubble, in those columns and in the state of the structural elements,” said Kolar.

The investigation could take months or longer, according to Allyn Kilsheimer, the structural engineer hired by the city of Surfside. It has begun examining the building and will use a meticulous computer-aided removal process to try to identify the cause or causes, he said.

“Unless it is known that a plane or a bomb caused it, sometimes it cannot be reduced to a single cause,” he said. “You don’t know what you’re going to end up with until you finish the whole study.”

A pool contractor who was repairing the condo’s pool 36 hours before its collapse told the Miami Herald that he had seen standing water and cracks in the concrete below the pool deck.

When he first entered the building, the pool area and upper lobby looked fine, but when he entered the basement garage below the pool deck, he claims he saw a lot of standing water and claims to have found cracks in the concrete from the pool equipment room, according to Miami Herald reporter Sarah Blaskey.

“He took a picture of that concrete to send to his boss, because he was there to do some cosmetic stuff in the pool, but he thought, ‘Wow, this is going to be a bigger job,’ he took a picture, sent it to his boss, ”Blaskey told CNN.

He noted that the photos were reportedly taken in the equipment room on the south side of the basement structure, rather than the north side, where the structure collapsed.

Families and friends await answers

Meanwhile, at least 11 victims have been identified:

• Stacie Fang, 54
• Antonio Lozano, 82
• Gladys Lozano, 80
• Manuel LaFont, 54
• Leon Oliwkowicz, 80
• Luis Bermudez, 26
• Anna Ortiz, 46
• Christina Beatriz Elvira 74
• Marcus Joseph Guara, 52
• Frank Kleiman, 55
• Michael David Altman, 50

The relatives of those who are still missing await any response they can get as the search continues.

“I have 100% faith in a lot of the things that are happening here,” Kevin Spiegel, Judy Spiegel’s husband, told CNN’s Wolf Blitzer. “Honestly, I think we all want more information.”

His daughter Rachel told CNN’s Don Lemon that she is nervous about the fires set off by the collapse and how the heat and smoke may be affecting rescue efforts. “I am very worried,” she said.

However, he told CNN that he was very optimistic about the teams of experts from abroad who have come to help with the rescue attempt. “There are so many teams from other countries coming and going to help us, which is fantastic.”

Ronit Felszer and Carlos Naibryf told CNN’s Alisyn Camerota on Monday that they are trying to be realistic about the possible outcome.

Carlos Naibryf said that his son “was a 21-year-old young adult. Sparkly. Wherever he went, he had an impact … now he’s at U. Chicago, majoring in physics. “

When Camerota asked the parents if they still believed in a miracle, Felszer shook his head.

“We want to believe in a miracle because we still do not have the physical presence, in part or in full, of our son,” he said.

“A miracle can come, yes, but we have to be very realistic,” the father told CNN.

Rescue conditions remain dangerous

As families cry and wait and officials investigate, the Mayor of Surfside said the main goal is to pull the victims out of the rubble.

“The number one priority here is to get these people out of the rubble and we are going to focus only on that. The second priority is supporting families, ”Charles Burkett told CNN’s John Berman on Monday night.

Miami Dade Fire Chief Alan Cominsky said the search efforts are “a slow process, but we are definitely making progress.” Rescuers are working 12-hour shifts and efforts have continued nonstop since the collapse early Thursday morning.

“These men and women are not stopping,” said Florida Finance Minister and State Fire Marshal Jimmy Patronis. “They still have a kind of drive and motivation that is really, really inspiring.”

Victims have been found in different areas as teams search through various search grids, rather than an isolated area, according to Cominsky.

At the beginning of the week, the weather and smoke conditions complicated the tasks of the rescuers, but now the conditions have improved although they remain dangerous in the search area.

“There is definitely a concern with the rain, and now the debris and possibly the landslide, so I mean it is an extremely dangerous situation,” he said. ” It is a very, very difficult situation, very, very challenging, and we are doing the best we can for what we are trained to do and we will definitely keep moving forward.

CNN’s Hannah Sarisohn, Rebekah Riess, Rosa Flores, Curt Devine, and Camille Furst contributed to this report.