Saying that the current investigation into how and why the twin towers fell on Sept. 11 is inadequate, some of the nation's leading structural engineers and fire-safety experts are calling for a new, independent and better-financed inquiry that could produce the kinds of conclusions vital for skyscrapers and future buildings nationwide.

Senator Charles E. Schumer and Senator Hillary Rodham Clinton, both of New York, have joined the call for a wider look into the collapses. In an interview on Friday, Mr. Schumer said he supported a new investigation ''not so much to find blame'' for the collapse of the buildings under extraordinary circumstances, ''but rather so that we can prepare better for the future.''

''It could affect building practices,'' he said. ''It could affect evacuation practices. We live in a new world and everything has to be recalibrated.''

Experts critical of the current effort, including some of those people who are actually conducting it, cite the lack of meaningful financial support and poor coordination with the agencies cleaning up the disaster site. They point out that the current team of 20 or so investigators has no subpoena power and little staff support and has even been unable to obtain basic information like detailed blueprints of the buildings that collapsed.