Engineers warned about structural damage to a Miami apartment block three years before its collapse, it has emerged.
The Champlain Towers South building in Surfside collapsed on Thursday, killing four people and prompting a search and rescue operation for the 159 people missing.
And concern about building safety has prompted an audit, which will take place within the next 30 days of nearby buildings approaching their 40-year review.
The collapsed building had been preparing for its recertification this year, having been built in 1981.
But a building further down the street, built by the same developer at around the same time, is likely to be looked at closely and could soon be evacuated.
Florida governor Ron DeSantis said: “I know they’re looking at (the sister building)… working with them, and I know they’re considering potentially evacuating them, but that’s something that ultimately the mayor is going to have to make the call on.
“I don’t know that there are indications there are any problems with that building but just given the similarities, given the same age, they think that may be something, so I think they may have an announcement on that today.”
The engineering report about the 12-storey Champlain Towers South, by Morabito Consultants in 2018, said waterproofing under the pool deck had failed, having been incorrectly laid flat instead of sloped, preventing water from draining away.
It warned that the failed waterproofing was “causing major structural damage” to the concrete slabs below.
When asked about it on Saturday, Miami-Dade mayor Daniella Levine Cava said: “We did not know about this report.”
The report did not warn of imminent danger and it is not clear if the damage was a factor in the collapse, but it recommended that the damaged slabs be replaced in what was expected to be an “extremely expensive” repair.
“Failure to replace the waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially,” the report said.
The report also said there was “abundant cracking” in concrete columns, beams and walls in the parking garage, including areas under the pool with “exposed deteriorating rebar”.
It criticised the standard of some previous repair efforts, saying they were marred by poor workmanship and “new cracks were radiating from the originally repaired cracks” under the pool deck.
It said some of the damage was minor but most of it “needs to be repaired in a timely fashion”.
The 84-page report was submitted to the town in April and it detailed a 40-year repair and restoration plan for the apartment building,
Satellite data from the 1990s has also showed the building was sinking between one and three millimetres each year, despite surrounding buildings remaining stable.
Florida International University professor Shimon Wdowinski said this could mean a structural compromise within the building, but it could also have indicated that the building was settling into the soil.
No more survivors have been found in the rubble of the collapsed apartment block, it was announced on Saturday.
Ms Cava said the search and rescue operation was continuing but a fire within the wreckage is making the work difficult.
She said: “We’re facing very incredible difficulties with this fire. It’s a very deep fire.
“It’s extremely difficult to locate the source of the fire.”