The announcement came amid reports that communication problems may have resulted in the high number of casualties.
The department has interviewed about 500 of its members since late September, following then-Commissioner Thomas Von Essen's order to examine how and why so many firefighters died that day.
"I knew right from the start that there was no way this Fire Department could extinguish six or eight floors of fire, fully involved, in a high-rise building," said Albert Turi, the deputy assistant chief of fire safety, according to an interview transcript obtained by The New York Times and reported in Wednesday's editions.
"It's just not possible, and we don't have the means to do it," he said.
The stability of the north tower, the first to collapse, was discussed "early on," said Chief Peter Hayden, then a deputy chief.
"But we were at a level of commitment," Hayden said. "We also received numerous distress calls. We realized we had a lot of dying and fire up there."
Several chiefs had set up a command board in the north tower lobby, to keep track of companies as they reported to the scene.
After the second plane hit the south tower, Joseph Callan, another ranking chief, radioed for units to come down to the north tower lobby. Several chiefs said communications problems may have prevented many from hearing the order. The chiefs called firefighters out several times, but "didn't get a lot of acknowledgment," Hayden said.
Hayden said the command center began to lose track of the companies. Some units even confused the two towers.
"The last report we had from anybody at all was that there were people heading up around the 48th floor. That was several minutes prior to this collapse. So we had people as high as the 50th floor while we had communications," Hayden said.
Fire Commissioner Nicholas Scoppetta said Wednesday the goal of the study would be to come up with recommendations to improve the department's response to catastrophic emergencies.
"The Fire Department is seeking the services of a consultant to perform an independent evaluation and study of the department's response and operations during and after the attacks," he said.
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