Sale of evidence condemned

The official report into the collapse of the twin towers is likely to heighten controversy over the decision by the New York authorities to auction most of the steel from ground zero for recycling.

Investigators were unable to study most of the joists and girders because so much had been sold to companies such as the New Jersey scrap merchant Metal Management, which bought 40,000 tonnes of for an undisclosed sum.

It sold on 10,000 tonnes for £1.2m to an Indian company which plans to use it to make furniture.

Gene Corley, who coordinated data collection from ground zero for the American Society of Civil Engineers, the co-sponsors of the study, recently told the science committee of the House of Representatives in Washington: "We told them we needed the steel. No one had the authority to ask them to preserve it."

Kenneth Holden, head of the city's department of design and construction, has denied the claim.