A massive amount of data and expert analysis on how and why the twin towers of the World Trade Center collapsed after being struck by two hijacked jetliners in the 11 September attacks may never be released.

The documents - compiled for a complicated court battle over insurance - may be the most comprehensive report yet, the New York Times says.

If they have answers and are not going to share them, I would be devastated

Monica Gabrielle, widow

The information includes three-dimensional computer modelling, maps, photos and videos, as well as analysis by engineering experts.

But a judge has ruled that if the lawsuit over the insurance payout for the attacks is settled, much of the information could remain sealed or be destroyed - as is common in such cases, the newspaper said.

The experts involved have all signed confidentiality agreements, and cannot reveal any of the information.

"We're obviously in favour of releasing the information, but we can't until we're told what to do," said Matthys Levy, an engineer and consultant in the case.

'Moral obligation'

The court battle is between real estate executive Larry Silverstein, whose companies owned a lease on the property, and a group of insurance companies.

Mr Silverstein claims that the plane crashes on 11 September were two separate terrorist incidents, which would make him entitled to $7bn, instead of the $3.5bn insurance firms are willing to pay out.

Relatives of the victims of the attacks have called for the information - which could be used to make new buildings safer - to be released.

Computer modelling was used to examine how the towers collapsed

"If they have answers and are not going to share them, I would be devastated," said Monica Gabrielle who, after losing her husband when the south tower collapsed, has joined the Skyscraper Safety Campaign.

"They have a moral obligation."

A spokesman for one of the insurance companies, Dean Davison of Industrial Risk Insurers, said his firm would try to make sure the information it has compiled would be available to "public authorities and investigative teams".

A spokesman for a government inquiry into the towers' collapse, being conducted by the National Institute of Standards and Technology (NIST), told the New York Times that access to the insurance-case documents might speed up their investigation, which is expected to take years.

The spokesman also said that the agency is in talks with Mr Silverstein about the documents, but that no information has been handed over.