A housing association has apologised after its attempts to bring down the iconic Red Road flats in Glasgow left two of the six towers largely intact.
It meant that about 2,500 people who live inside the exclusion zone set up for the demolition faced delays in being allowed back into their homes.
Glasgow Housing Association apologised for the delays.
Demolition experts hope to begin bringing down the two remaining towers later this week.
An independent technical review of the blowdown is being carried out.
The towers, which were the tallest residential buildings in Europe when they were built as social housing in the 1960s, were being demolished as part of GHA's plans to regenerate the Balornock and Barmulloch areas of the city.
Residents were allowed to return to their homes shortly before nightfall after safety checks had been carried out.
GHA said in a statement: "The original plan for the demolition was that 10 floors of the blocks would remain for dismantling, post blowdown, by machine. However, this did not go completely to plan.
"Over the next few days the contractors, Safedem, will carry out a review to determine the best way of now completing the demolition.
"Residents began moving back into their homes shortly after 6pm, just over an hour later than originally planned. We sincerely apologise to everyone involved for this delay and any additional inconvenience caused."
Safedem managing director William Sinclair said: "Two of the six blocks involved in Sunday's blowdown didn't fall exactly as planned. Instead of 10 storeys remaining in all of the blocks, we now have 13 still standing at Red Road Court and 11 at Petershill Drive.
"However, we will proceed with our original plan of dismantling all of the blocks using routine machine demolition methods. Preparations for this are already under way and high-reach machinery will begin taking down what's left of the blocks this week."
Local MSP Patricia Ferguson told BBC Radio's Good Morning Scotland programme that she had been assured the two remaining blocks were stable.
She added: "I do think we need to find out why it didn't work yesterday, and speaking to GHA I have been reassured that there will be an independent inquiry into why that is the case".
Mark Anthony, the editor of demolitionnews.com, said it was not particularly unusual for large demolition projects to go wrong.
He said: "A lot of the time when you are taking down a building it is by explosive or mechanical means and you haven't got a lot of information on how these structures were built.
"So if you are relying on gravity all it would take is an exceptionally strong part of that building and it will hold it together.
"We have seen these around the world, where literally the entire building has stayed upright and it has made no difference at all."
Two previous demolitions have taken place at Red Road in 2012 and 2013. The towers were once home to about 5,000 people.