Firefighters and police officers struggling to save thousands of people in the World Trade Center complex on Sept. 11, 2001, were severely hampered by communication problems and turf battles, and almost no one believed that the twin towers were in danger of collapsing that morning, according to a report issued Tuesday by the commission investigating the Sept. 11 attacks.

In an emotional and often tense day-long hearing in Manhattan attended by hundreds of survivors and victims' relatives, several members of the commission sharply criticized current and former New York City officials for not adequately planning for a large-scale terrorist attack on skyscrapers, especially given the bombing of the World Trade Center in 1993. Some members also criticized an emergency-management plan unveiled last week by Mayor Michael R. Bloomberg (R), with Vice Chairman Lee H. Hamilton calling it "a prescription for confusion."

According to a painstaking, 26-page report by the commission's investigative staff, panic-stricken workers in the trade center were given conflicting information on the day of the attacks, including repeated instructions not to evacuate. Many emergency workers were uninformed or misinformed about the rapidly deteriorating situation, and there was no plan in place for rescuing those caught above the fire, the report found.

But the searing account also made it clear that, despite their history of feuding, officers and firefighters from the New York City Fire Department, the New York City Police Department and the Port Authority Police Department struggled valiantly, and in many cases against the odds, to save lives before the towers fell.

"That day we lost 2,752 people at the World Trade Center; 343 were firefighters," Deputy Assistant Fire Chief Joseph Pfeifer told investigators in videotaped comments that were played at Tuesday's hearing. "But we also saved 25,000 people. And that's what people should remember, because firefighters and rescuers went in and they knew it was dangerous, but they went in to save people. And they saved many."

The report by the National Commission on Terrorist Attacks Upon the United States, as the panel is formally known, highlighted many of the problems made evident by previous reports, including transcripts of radio transmissions and telephone calls released last year by the Port Authority of New York and New Jersey, which owned the trade center. But the commission's findings provide perhaps the most definitive and detailed account of the difficulties rescuers encountered.

The report was released at the start of two days of hearings at New School University in Greenwich Village, just 11/2 miles from Ground Zero. Unlike many of the commission's recent hearings in Washington, which focused on policy decisions and intelligence missteps by the federal government before Sept. 11, Tuesday's testimony concerned the attacks and the performance of local emergency responders.

The hearing began with a somber, dramatic presentation by the panel's staff members, who interspersed a reading of the report with videotaped testimony and footage of the attacks. Many who packed the Tishman Auditorium on West 12th Street, clutching pictures and posters of loved ones, were weeping by the end.

Much of the video aired Tuesday came from a French filmmaker, Jules Naudet, who was working on a documentary about New York firefighters and accompanied Pfeifer that day.

The hearing also featured a series of sharp exchanges between former New York fire and police officials and panel members, who were clearly frustrated by what they view as the city's inefficient system for handling emergencies. Commission member John F. Lehman (R), a former secretary of the Navy, argued that the lack of "command and control" in New York was a "scandal" that "is not worthy of the Boy Scouts, let alone this great city." He also said Bloomberg's plan "simply puts in concrete a clearly dysfunctional system."

Thomas Von Essen, who was New York's fire commissioner at the time of the attacks, responded angrily. "There's nothing scandalous about the way New York City handles its emergencies. . . . I think it's outrageous that you'd make a statement like that," he said.

The exchanges frequently prompted booing or clapping from scores of victims' family members, many of whom appeared to be skeptical of fire and police officials.

In their report, commission investigators stopped short of assigning blame in many instances and did not speculate about how many lives might have been saved if things had gone differently. The report also included chilling details, such as the finding that "the first FDNY fatality of the day occurred at approximately 9:25 a.m. when a civilian landed on a fireman on West Street."

According to the report, scores of workers in both towers rushed upward, unaware that doors to the skyscraper roofs were locked and that rescue helicopters would not be able to navigate the heat swells and rooftop antennas to rescue them. No one heard an evacuation announcement from the fire department minutes after American Airlines Flight 11 slammed into the North Tower at 8:46 a.m., because the public address system was destroyed in the crash.

Early decisions were based on standard operating procedures for high-rise fires, which call for occupants to remain in place or move only a couple of floors to await rescue. There was no plan for reaching those caught above the fire, even though more than a dozen people had been saved by helicopter in the 1993 bombing.

Investigators, working from recordings and transcripts of emergency calls and radio traffic that morning, also concluded that 911 operators frequently gave misleading or inaccurate information, and that numerous callers could not get through or were put on hold.

"Calling 911 on September 11 was a pointless exercise," said commissioner Slade Gorton, a former Republican senator from Washington. "The 911 operators were clueless. . . . They didn't know as much as someone sitting home watching television."

By 9 a.m., fire officials had decided that the blaze in the North Tower could not be contained and that evacuation was the only choice.

"Several floors of fire would have been beyond the fire-extinguishing capability of the forces that we had on hand," Assistant Fire Chief Peter Hayden told investigators. "So we determined very early on that this was going to be strictly a rescue mission. We were going to evacuate the building, get everybody out, and then we were going to get out. . . . I had a strong inner sense throughout this entire operation that we were going to lose people this day."

In the South Tower, meanwhile, workers were initially instructed through an announcement and other means to stay -- or, if they were attempting to leave, to return to their offices -- largely because of concerns about fiery debris and other hazards from the crash into the North Tower. One fire chief also told investigators it was unimaginable that a second plane might hit the South Tower. At 9:03 a.m., United Airlines Flight 175 did just that.

"I am looking to the direction of the Statue of Liberty, and I am looking at an airplane coming, eye level, eye contact, towards me -- giant gray airplane," recalled Stanley Prainmath, a bank assistant vice president whose office was on the 81st floor. "I am still seeing the letter U on its tail, and the plane is bearing down on me. I dropped the phone and I screamed and I dove under my desk. It was the most ear-shattering sound ever. The plane just crashed into the building. The bottom wing sliced right through the office, and it stuck in my office door 20 feet from where I am huddled under my desk."

Prainmath was rescued by Brian Clark, president of Euro Brokers Relief Fund, who pulled him from the rubble. "Come on," Clark said, putting his arm around Prainmath. "Let's go home."

At 9:59 a.m., the South Tower collapsed, but because of communication glitches and other problems, many rescue workers and employees in the North Tower did not realize it.

"To our knowledge, none of the evacuation orders mentioned that the South Tower had collapsed," panel investigators wrote. "Firefighters who received these orders lacked a uniform sense of urgency in their evacuation."

The panel's hearing will continue Wednesday morning with testimony from Bloomberg, former New York mayor Rudolph W. Giuliani, Homeland Security Secretary Tom Ridge and Edward P. Plaugher, chief of the Arlington County Fire Department. Several commissioners have lauded the response to the Pentagon crash on Sept. 11.

The staff uses video of the attacks in presenting its findings on emergency preparedness and response to the panel.