SURFSIDE, FLORIDA (NYTIMES) - Mr Pablo Rodriguez was finding it increasingly difficult Sunday (June 27) to believe that his mother and grandmother were still alive.

"I wish I could say yes, but the answer is no," said Mr Rodriguez, 40, of Miami, who said that his mother, Ms Elena Blasser, 64, and his grandmother Ms Elena Chavez, 88, had been in a penthouse unit above the Champlain Towers South condominium building when it collapsed early Thursday morning.

But Mr Douglas Berdeaux held out a faint glimmer of hope for his sister-in-law Elaine Sabino, a flight attendant who lived in another penthouse suite. Mr Berdeaux said he had participated in a Zoom call Sunday morning with emergency officials, among them a member of an Israeli search-and-rescue team who had come to Florida to help - and who relayed the story of victims who had been found alive more than 100 hours after an earthquake in Haiti.

"We're just hoping and praying that a miracle will happen," Mr Berdeaux said.

But in general, hope was fading fast Sunday among families of the missing, as rescuers continued to search the precarious debris pile of the partially collapsed condo complex.

Workers pulled large chunks of debris off the top of the pile with the aid of heavy equipment, bored a massive trench underneath, and deployed crews from around the world with expertise in scouring buildings mangled by earthquakes and rockets.

But after a few early rescues, the crews as of Sunday afternoon had found only a handful of bodies and scattered human remains amid the Florida wreckage, bringing the total official death toll to nine. More than 150 people remained unaccounted for. It felt as if a window was closing.

"I can tell you that hope is somewhat diminishing, as you can imagine," said Rabbi Sholom Lipskar of The Shul, the Orthodox Jewish congregation where numerous members were presumed missing.

"There's a lot of frustration. I'd say it's turning into a little bit of anger, because they haven't found people yet."

As non-profit organisations made psychologists available for family members navigating a fourth day of uncertainty, search-and-rescue officials turned to structural engineers to help them safely navigate the imposing and unstable tangle of concrete, flooring, wires and personal effects.

The rescue effort has been further hampered by the presence of noxious smoke, a fire that raged deep inside the pile until noon Saturday, and summer storms that have occasionally brought lightning, forcing intermittent breaks in the action to comply with federal workforce guidelines.

"It's an extremely difficult situation," Mr Alan Cominsky, the Miami-Dade County fire chief, said in a news conference. "Our rescue teams are working nonstop, doing all that we can, searching every area, every bit of hope, to see if we can find a live victim."

The 24-hour rescue operation at the beachfront building, Champlain Towers South, now involves more than 300 emergency personnel and the US Army Corps of Engineers. More people and personnel, officials said, was not what they needed.

"We are not resource-poor," Mayor Charles Burkett of Surfside said Sunday morning on ABC News. "We don't have a resource problem, we've had a luck problem. We just need to start to get a little more lucky right now."

Mayor Daniella Levine Cava of Miami-Dade County said in a Sunday morning news conference that more bodies and remains were recovered overnight when rescuers began to dig a trench into the pile of debris.

She said the trench would eventually be 125 feet (38m) long, 20 feet wide and 40 feet deep.

Mr Roy Hausmann, a board member of Cadena International, a Jewish humanitarian aid group, said that a well-seasoned, seven-member search-and-rescue team from his organisation arrived in the Miami area from Mexico on Thursday, bringing special equipment that he said could "detect movement, breathing and life signals of potential survivors up to a depth of 35 to 40 feet."

On Sunday morning, a number of family members gathered, as they had in days past, at the nearby Grand Beach Hotel, which has been designated a "reunification centre"- although no reunifications took place. Later in the day, county officials loaded some of them onto a pair of buses and took them to the disaster site, where they could observe the rescue work up close.

As the buses, escorted by the police, arrived at the scene, acrid smoke lingered from fires beneath the rubble pile. A crane lifted heavy chunks of the building and moved debris from the site onto dump trunks.

Two women carrying flyers about missing residents walked past the police to the chain link fence near the scene of the collapse that had become a makeshift memorial.

Rabbi Joseph Galimidi of the Edmond J. Safra Synagogue, in nearby Aventura, Florida, followed them to the memorial and prayed. It was his first visit.

"Someone asked me if I had lost a relative," Rabbi Galimidi said. "I did know some of the people. We used to be neighbours."

He was struck by the photos of missing family members on the fence. "It reminded me of 9/11," he said. "We say that seeing is believing. When you come here and see all of this - we hope that with every hour that goes by, that we will hear better news."

Concern about the stability of other buildings has spread across South Florida, with officials promising to check them more closely and pass laws to assure that similar tragedies do not occur.

Ms Levine Cava, the Miami-Dade County mayor, announced a 30-day audit of all buildings 40 years and older under the county's jurisdiction, which does not include cities like Miami and Surfside, where the building fell.

The concern about building safety has been highest at Champlain Towers North, the sister condo complex nearby, which has the same developer and same design and was built around the same time.

Inspectors from the town and county spent several hours conducting an initial inspection of the North tower Saturday, according to the town and the condo board, and it was eventually decided that an evacuation was not necessary there.

"The building is very sound," said Ms Hilda Gandelman, a board member for the north tower said Sunday. "Everything is sound."

Although family members struggled with the slow pace of the search, the tragedy could also feel, simultaneously, as if it were unfolding too fast.

Mr Alfredo Lopez, 61, had managed to race out of the building just after the collapse Thursday morning, while carrying an elderly neighbour to safety on his shoulder.

On Sunday morning, Mr Lopez, who runs a heavy machinery export business, attended Mass at nearby St. Joseph's Catholic Church. He was suffering, he said, from survivors' guilt; the grief, he said, was still coming "in spurts."

He said he had lost everything: "I got no money. I got no credit cards. I got no ID. Nothing."

Mr Lopez said he planned to go to work Monday, in the clothes he was wearing. But he was still replaying, in his head, the moment he opened the door of his apartment and stared into a yawning void that just moments before had been his hallway.

"There was no apartment on the left side, no apartments in front of me, no hallway, no wall, nothing," he said. "That whole area crumbled, how fast -. I don't know how that happened. It just completely disappeared."