The commission's staff presented a detailed, almost minute-by-minute account of the rescue efforts as the panel opened two days of hearings in New York Tuesday.

Commission staff members showed dramatic videotaped testimony from firefighters, police and civilians who evacuated the Trade Center's twin 110-story towers before they collapsed.

Fire chiefs who were inside the North Tower said they were unaware the South Tower had collapsed just before 10 in the morning that Tuesday.

The report says that when the chiefs decided the North Tower should be evacuated, many rescue workers did not hear the command because they were using different radio channels or did not have radios at all.

It says none of the evacuation orders mentioned that the South Tower had collapsed, and that rescue workers in the north building "lacked a sense of urgency" to vacate.

Hijacked airliners were flown into the towers, killed 2,749 people in all, including more than 300 firefighters.

The panel's report says a civilian in the South Tower's upper floors had warned an emergency phone operator that the building was starting to collapse, but that the operator did not get the right message across to police.

It says a helicopter pilot warned that the North Tower appeared ready to fall, but that there was no way to get this information to the chiefs inside.

After the report, the commission began hearing testimony from New York's current and former police and fire commissioners.

During a second day of hearings Wednesday, the panel will hear from former New York Mayor Rudolph Giuliani, his successor Michael Bloomberg, and Homeland Security Secretary Thomas Ridge.