SURFSIDE, Fla. (AP) - Rescue workers digging feverishly for a fifth day Monday stressed that they could still find survivors in the rubble of a collapsed Florida condo building, a hope family members clung to even though no one has been pulled out alive since the first hours after the structure fell.

The death toll rose by just four people Sunday, to a total of nine confirmed dead. But more than 150 people are still missing in Surfside.

Families of the missing rode buses to a site nearby from which they could watch teams at work Sunday: firefighters, sniffer dogs and search experts employing radar and sonar devices.

Andy Alvarez, a deputy incident commander with Miami-Dade Fire Rescue, told ABC’s “Good Morning America” on Monday that rescuers have been able to find some voids inside the wreckage, mostly in the basement and parking garage areas.

“We have over 80 rescuers at a time that are breaching the walls that collapsed, in a frantic effort to try to rescue those that are still viable and to get to those voids that we typically know exist in these buildings,” Alvarez said.

“We have been able to tunnel through the building,” Alvarez added, and big cranes have helped rescuers lift “huge pieces of concrete” off the pile. “This is a frantic search to seek that hope, that miracle, to see who we can bring out of this building alive,” Alvarez said.

He said rescuers, like the families, are still hoping for good news. “You’ve gotta have hope and you’ve gotta have faith,” he said.

Israeli Diaspora Affairs Minister Nachman Shai, head of a humanitarian delegation from Israel that includes several search-and-rescue experts, said the professionals have told him of cases where survivors were found after 100 hours or more.

“So don’t lose hope, that’s what I would say,” he said.

Some families had hoped their visit to the site near the 12-story building would enable them to shout messages to loved ones possibly buried deep inside the pile. As they returned to a nearby hotel, several paused to embrace as they got off the bus. Others walked slowly with arms around each other back to the hotel entrance.

“We are just waiting for answers. That’s what we want,” said Dianne Ohayon, whose parents, Myriam and Arnie Notkin, were in the building. “It’s hard to go through these long days and we haven’t gotten any answers yet.”

The building collapsed just days before a deadline for condo owners to start making steep payments toward more than $9 million in repairs that had been recommended nearly three years earlier, in a report that warned of “major structural damage.”

Authorities on Sunday identified the additional four people that had been recovered as Leon Oliwkowicz, 80; Christina Beatriz Elvira, 74; Ana Ortiz, 46; and Luis Bermudez, 26. The number of people left unaccounted for was 152, said Miami-Dade Mayor Daniella Levine Cava. The last live person rescued was on Thursday, just hours after the collapse.

Miami-Dade Assistant Fire Chief Raide Jadallah explained that conditions at the site - the building pancaked when it fell - have frustrated crews looking for survivors. Alan Cominsky, chief of the Miami-Dade Fire Rescue Department, said his team is holding out hope of finding someone alive, but must continue to move slowly and methodically.

“The debris field is scattered throughout, and it’s compact, extremely compact,” he said, noting that teams must stabilize and shore up debris as they go.

“We can’t just go in and move things erratically, because that’s going to have the worst outcome possible,” he said.

Among the tools rescuers used was a microwave radar device developed by NASA’s Jet Propulsion Lab and the Department of Homeland Security that “sees” through up to 8 inches of solid concrete, according to Adrian Garulay, CEO of Spec Ops Group, which sells them. The suitcase-size device can detect human respiration and heartbeats and was being deployed Sunday by a seven-member search-and-rescue team from Mexico’s Jewish community.