By Emma Simpson BBC correspondent in New York

A public meeting is being held in New York on Monday, to help identify lessons to be learned from the collapse of the World Trade Center.

The meeting has been organised by a government agency which is due to begin a lengthy investigation into all the technical and safety issues raised as a result of the disaster.

Future skycrapers may be built differently

Victims' families have been invited for the first time to have their say into what is expected to be a multi-million dollar investigation.

Despite the widely accepted notion that no skyscraper could have withstood a fuel-laden jet slicing into its core, relatives say there are still many technical questions to be answered.

For instance, they want to know if better fire-proofing materials and evacuation procedures could have resulted in more people escaping from the buildings.

Regulations

An initial report has found that automatic sprinklers were disabled by the impact of the crash, that exit stairwells were cut off and that much of the material used to protect critical steel beams had been dislodged.

The families have been pushing for a comprehensive investigation.

Researchers from America's National Safety Standards Institute are now for waiting approval from Congress so they can begin trying to find out precisely how and why the towers collapsed.

The investigation is expected to take two years and cost about $16m.

Investigators will also look into whether new regulations are needed for those involved in designing and building skyscrapers of the future.