DES MOINES, Iowa >> An Iowa task force has completed its search for survivors at the site of a partially collapsed Davenport apartment building without finding three missing people who are feared dead, authorities said Friday. The focus has shifted to shoring up the structure so recovery efforts can begin.

The remains of the six-story apartment building were constantly in motion in the first 24 to 36 hours after it collapsed on Sunday, which officials said posed a risk to rescuers who were trying to search for survivors.

“We do what the building tells us to do,” Rick Halleran, the task force’s Cedar Rapids division chief, said of the delay in searching the building.

City officials earlier this week said that Brandon Colvin, Ryan Hitchcock and Daniel Prien were unaccounted for and had “high probability of being home at the time of the collapse.” All three have since been listed in the National Database of Missing Persons.

The state task force was mobilized and on site to first search for survivors and then secure the structure, Halleran said. He said the search for survivors was completed Thursday evening after electrical equipment connected to the building were controlled. The state’s search and rescue team, search dogs and cameras were used in the search Thursday.

Officials fear the unstable building will eventually collapse on its own. Adding to the challenge is a giant pile of brick and steel at the base of the building that is helping to hold up the structure but also may contain the remains of people killed in the collapse.

“We are doing the best we can to balance the building conditions and the safety of our responders,” said Fire Chief Mike Carlsten. He said conditions have forced a response that may take “days and weeks” instead of what ideally would have been minutes or hours after the collapse.

Mayor Mike Matson has said the debris pile “could be a place of rest for some of the unaccounted” and stressed the city would be sensitive about those remains, comparing work at the site to an archeological dig.

Work to bring down the building comes amid questions about why neither the owner nor city officials warned residents about potential danger even after a structural engineer’s report issued last week indicated a wall of the century-old building was at imminent risk of crumbling.

Documents released Wednesday night show city officials and the building’s owner were warned for months that parts of the building were unstable.

Current and former residents speaking with The Associated Press described concerns about interior cracks on the wall that ultimately collapsed that were reported to building management. There also have been numerous complaints to the city over the years about issues including lack of heat, hot water or proper insulation.

The day before the collapse, the operations director of Downtown Davenport Partnership, an organization affiliated with the city’s chamber of commerce, called 911 to report concerns that a local contractor had relayed, the Quad City Times reported. The newspaper reported that fire officials who responded to the emergency call spent less than five minutes at the scene.

“Do I have regrets about this tragedy and about people potentially losing their lives? Hell yeah. Do I think about this every moment? Hell yeah,” Matson said Thursday. “I have regrets about a lot of things. Believe me, we’re going to look at that.”

City officials said Thursday that they did not order an evacuation because they relied on the engineer’s assurances that the building remained safe. Matson promised to improve inspections and to investigate what happened.

Scott County prosecutor Kelly Cunningham cautioned Friday against assuming a criminal prosecution is appropriate, saying an independent investigation needs to be conducted into the cause of the building’s structural failure, and right now it’s in the city’s jurisdiction.

The building collapsed shortly before 5 p.m. Sunday. Rescue crews pulled seven people from the building in their initial response and escorted out 12 others who could walk on their own. Later, two more people were rescued, including a woman who was removed from the fourth floor hours after authorities said they were going to begin setting up for demolition.

Davenport Police Chief Jeff Bladel said transient people also often entered the building but there was no indication anyone else was inside and missing. Asked at a news conference Friday if any human remains have been found in the building, Matson said, “We can’t disclose that yet.”

Andrew Wold, the building’s owner, released a statement dated Tuesday saying “our thoughts and prayers are with our tenants.” He has made no statement since then, and efforts to reach him, his company and a man believed to be his attorney have been unsuccessful.

County records show Davenport Hotel L.L.C. acquired the building in a 2021 deal worth $4.2 million.

Tenants had complained to the city in recent years about a host of problems they say were ignored by property managers, including no heat or hot water for weeks or even months at a time, as well as mold and water leakage from ceilings and toilets. While city officials tried to address some complaints and gave vacate orders to individual apartments, a broader evacuation was never ordered, records show.

City officials ordered repairs after they found seven fire code violations on Feb. 6. However, they were told three weeks later by building maintenance officials that “none of the work was completed,” records show.

Rich Oswald, the city’s director of development and neighborhood services, said Thursday that the city’s chief building official, Trishna Pradhan, voluntarily resigned after the collapse.

Pradhan had visited the building on May 25, and erroneously reported it had “passed” an inspection in notes in the city’s online permitting system, Oswald said. She attempted to change the inspection result to “incomplete” on Tuesday — after the collapse — but a technical glitch instead listed the outcome as “failed,” he said, adding that the “incomplete” status is correct since the repair work was unfinished.

Calls and text messages to Pradhan were not immediately returned.

Assistant City Attorney Brian Heyer said he doesn’t know whether the city had considered earlier civil enforcement action to protect residents. Only after the collapse did the city file a civil infraction seeking a $300 fine against Wold for failing to maintain the structure in a safe manner. He will be required to pay for the cost of demolition, Heyer said.

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Associated Press reporters Ryan J. Foley contributed from Iowa City and Summer Ballentine contributed from Jefferson City, Missouri.