NBC publicly apologized last night for secretly using incendiary devices to stage a fiery crash involving a General Motors pickup truck and announced that it had settled a day-old lawsuit filed by the auto maker.

In an abrupt reversal of the network's earlier insistence that it had done nothing wrong, Jane Pauley, co-host of "Dateline NBC," told viewers that "we agree with General Motors that we should have told our viewers" about the incendiary devices and that it was "a bad idea from start to finish."

Co-host Stone Phillips added: "We deeply regret that we included the inappropriate demonstration in our 'Dateline' report. We apologize to our viewers and to General Motors. We have also concluded that unscientific demonstrations should have no place in hard news stories at NBC."

The announcement, shortly before 11 p.m., came amid growing criticism from industry executives and media analysts that NBC had wrecked its credibility in what will surely be remembered as one of the most embarrassing episodes in modern television history.

GM sued Monday, just days after an Atlanta jury ordered the company to pay $105 million to the parents of a 17-year-old who died in a fiery crash involving a GM pickup.

NBC News president Michael Gartner insisted Monday that the "Dateline" program last November was fair and accurate and that GM was merely trying to divert attention from its allegedly unsafe trucks, made between 1973 and 1987. GM officials charged that the test was "rigged" and that NBC had deceived its audience.

NBC attached remote-controlled model rocket engines to the truck to ensure it would catch fire. Network officials retreated behind a curtain of no comments yesterday while their attorneys were hammering out a settlement with GM.

NBC spokeswoman Tory Beilinson said the network has agreed to pay GM's costs in investigating the matter. Asked if anyone would be fired or disciplined, she said the question was "premature" but added: "We will now try to determine where our process went awry."

Earlier in the day, Don Hewitt, executive producer of CBS's "60 Minutes," said: "You can do anything in television -- if you level with the audience. They knowingly did violence to the truth, and they did not broadcast what their viewers thought they were seeing."

"On television, seeing is believing," said Robert Lichter, director of the Center for Media and Public Affairs. "If you set it up so people aren't seeing what they believe they are, they may never believe you again. If you're making sure a fire starts, you should tell your viewers that."

In their on-air mea culpa last night, Pauley and Phillips read a series of statements by GM and said the network would not contest them. Phillips said that the staged crash "was not representative of an actual side-impact collision" and that NBC's replacement of the truck's original gas cap caused the leak that started the fire.

NBC also did not dispute the auto maker's contention that the crash took place at a higher speed than the 30 miles per hour claimed by "Dateline."

The journalistic issue in the NBC broadcast of Nov. 17 is not the safety of the older-model GM trucks.

Nor is the issue whether incendiary devices are standard procedure in safety tests. Vincent Brannigan, a professor at the University of Maryland's Department of Fire Protection Engineering, said that "when you are doing fire testing, you always use igniters. All fire tests use igniters."

The real question, media analysts said, is why NBC failed to disclose that its dramatic footage, aired during "sweeps week," involved the use of spark-producing devices. An NBC policy manual states that "staging of any kind is prohibited."

One NBC official said Gartner was not consulted about the crash test but that "Dateline" producers did not consider it staging.

The segment -- called "Waiting to Explode?" -- was produced by Robert Read, a former producer for "Inside Edition" and "20/20," and reported by Michelle Gillen. It was seen by an estimated 11 million households.

Gartner said in a letter to GM Monday that a dangerous crash involves both sparks and leaking gasoline, and that "a particular crash might not also produce sparks. . . . The sparking device was intended to simulate sparks which could occur in a collision."

Gartner said "Dateline" made no mention of the incendiary devices because its experts concluded that the fire was caused by a spark from the broken headlight of the oncoming car.

Sanford J. Ungar, dean of American University's School of Communication, found this explanation unconvincing. "Why do you have to hide it if it's a standard part of the crash test?" he said. "It's just deplorable. I don't know where the line is, but I know this crosses it."

"Putting those little sparklers under the truck . . . is perpetrating a fraud," said Stephen Klaidman, a fellow at Georgetown University's Kennedy School of Ethics. "It is just beyond the pale."

On the Nov. 17 broadcast, one test car crashed into a GM truck at what NBC said was "about 40 miles per hour," but did not cause a fire. During a second test, which the program said occurred at "around 30 miles per hour," the GM pickup burst into flames, a scene that was replayed in slow motion.

The auto maker's investigation took on the air of a detective story. After getting a tip that NBC had used model rocket engines in the crash, GM asked to examine the four vehicles. "Dateline" said the trucks had been junked and were no longer available, but GM employees found them near the crash site, outside Indianapolis, and purchased them. The company said two model rocket engines were still taped to the chassis of one truck.

"It doesn't help that NBC apparently tried to hide the evidence," Lichter said. "When they want to do a story, it's the public's right to know. When someone wants to check the evidence, they stonewall just like any big corporation."

The controversy has morale at the network deflating like a punctured tire. Some NBC reporters and producers said that "Dateline" is typical of a sensational, ratings-driven magazine show that sometimes falls short of network news standards.

"Everyone's pretty horrified," one NBC staffer said. "We've all been told over and over again, no staging. The basic rule is, if it isn't happening, you cannot make it happen."