Experts said it's unlikely a single issue caused the deadly collapse of the Champlain Tower South condominium complex, but a confluence of factors may have.

       The oceanfront Surfside, Florida, complex, which was built in the 1980s and up for its 40-year recertification, collapsed Thursday. At least four people are dead, and 159 are still missing, officials said Saturday.

       Jason Borden, a structural engineer who conducted a site survey at the building last year, said the findings of a structural field service report from 2018, publicly released overnight Friday, described "abundant cracking and spalling" and "failed waterproofing" that could have contributed to the collapse.

       Gianrigo Marletta/AFP via Getty Images

       The wreckage of a partially collapsed building in Surfside north of Miami Beach, Fla., June 25, 2021.

       "Any of those items by themselves are unlikely to have been the sole reason why the collapse happened, but those combined with other things also could have been an issue that added up to the overall net result," Borden told ABC News.

       MORE: Surfside building collapse latest: 2018 structural report shows evidence of cracks, flooding

       Miami-based architect Kobi Karp agreed, saying, the collapse likely resulted from "a collection of bad things."

       "There are certain deficiencies to the existing structure which were not maintained," Karp added.

       Gerald Herbert/AP

       Rescue workers search the rubble at the Champlain Towers South Condo, June 25, 2021, in the Surfside area of Miami.

       Construction on Champlain Tower South was just starting to get underway following on the results of that 2018 report, and work was being done to replace the roof when the collapse happened, Ken Direktor, a lawyer for the condominium's board, told ABC earlier this week.

       MORE: Survivors recount horror of Surfside building collapse: 'We knew it was a race against time'

       Surfside Vice Mayor Tina Paul, who was on the commission at that time, told ABC News that she was not aware of the 2018 report at the time it was completed.

       "Unfortunately, it appears nothing was done," Paul said. "The town is deeply concerned for the safety of all our condo residents and their homes, and we have brought in a structural engineer team to analyze what happened and look at our other buildings."