A botched demolition of the Red Road flats that left two partially standing happened because they were "too tough", a report has found.

An independent review of the demolition of the Glasgow tower blocks last October found contractor Safedem used "good practice" during the process but "underestimated the robustness" of the buildings.

Glasgow Housing Association said at the time the process "did not go completely to plan" after four of the six multi-storey flats remained partially standing.

It meant some residents were unable to return to nearby homes when planned.

Up to 2500 people were kept from their homes surrounding the site due to the failed demolitions, the review found.

The demolition firm Safedem employed an "extremely experienced explosives engineer" who was a "recognised expert" in the field and carried out jobs around the world.

The report looked at drawings of the flats from the city archives and found a number of discrepancies between the original plans and the eventual construction.

Primarily, it found the column sizes differed from those shown on the drawings and that the structures were reinforced with steel.

The report stated: "Safedem appear to have underestimated the robustness of the buildings.

"Whether this was from the explosives view point, the structural appraisal view point or a combination of both, is unclear."

"It should be noted that the steel-framed residential structures are relatively uncommon in the UK. Most multi-storey high rise flats are constructed in concrete.

"Unlike concrete structures, steel frames do not collapse under impact from the debris above and tend to be more robust.

"Hence, pre-weakening is essential not only to minimise explosives but to ensure critical members are removed and prevented from providing secondary support."

The report added: "The partial collapse of both 123 Petershill Drive and 10 Red Road Court were due to the variances in their construction and the exceptional difficulties in predicting the behaviour of these unique buildings.

"In this instance, Safedem had carried out detailed surveys and noted a number of discrepancies between the surveyed buildings and the design drawings and therefore appear to have followed good practice.

"Bearing in mind these discrepancies, it would have been reasonable for their designers to take a cautious view of the structures and err on the safe side, regarding pre-weakening."

Following the failure, the towers were brought down using high-reach machinery.