Steve Capus, the president of NBC News, strongly defended their decision to broadcast the material.

“The news-value question is long gone,” Capus said. “Every journalist is united on this. You can tell by their actions.” He referred to the widespread use of the material NBC released by virtually every other news organization in the country.

Still, NBC announced early in the day that it would limit its use of the images across NBC News, including MSNBC, to no more than 10 per cent of its airtime.

NBC received a package in the mail on Wednesday from the gunman, Cho Seung-Hui. The material included 23 pages of writing and photographs and videos on DVD. Cho made rambling threats and was depicted brandishing guns and other weapons.

Families of some of the victims, some law enforcement officials and executives from competing television news organisations have accused NBC of being insensitive or exploitative in the way it presented the materials on the air.

But in an interview, Capus described a daylong process of evaluation on Wednesday, involving numerous NBC executives and news staff members, some of whom, including Matt Lauer, the Today show anchor, expressed some reservations about putting the statements of Cho on TV.

Lauer said on his program yesterday, “Let’s be honest, there are some big differences of opinion right within this news division as to whether we should be airing this stuff at all, whether we’re taking the right course of action.”

Numerous NBC executives had been involved in the process, Capus said, including the president of the company, Jeff Zucker, and the head of its standards division, David McCormick. Along with the management and many of the staff members of the news division they had weighed all the factors before deciding how to proceed, Capus said.

“It’s not every day we get a story like this,” Capus said. “We went over it for seven and a half hours. We didn’t rush it on the air. We weren’t promoting it. We weren’t trumpeting it all day. It was extraordinary, and that’s how we treated it.”

One law enforcement official said that the FBI had not publicly taken issue with NBC’s decision to broadcast the material because it was not the agency’s place. “It was their property, and it was sent to them,” the official said, referring to NBC. “And they’re in the news business.”

FBI agents sought to determine whether the package contained material beyond what might have been recovered in Virginia. Capus said the network had expected some of the criticism heard yesterday from family members and friends of the victims — in one example several family members canceled an appearance on Today to protest the network’s use of the material.