The first word many U.S. journalists heard about a Nicaraguan "incursion" into Honduras was not through an official announcement but almost as an aside.

Assistant Secretary of State Elliott Abrams, at a White House briefing about Central American policy, said in response to a question from a reporter Monday morning that there was "preliminary information" about "a very large Sandinista incursion into Honduras."

For some reporters, the response was baffling. "Do we have to ask a question to find out about World War III?" wondered one reporter. Was it an invasion -- a four-alarm news story? Or was it nothing? Was it an administration ploy on the eve of an important Senate vote on aid to the anti-Sandinista rebels?

Within hours, Honduran officials had denied reports of fighting or said they knew nothing about 1,500 troops crossing their border.

Thus began a week of confusion about a battle in a remote mountainous area of Central America.

In contrast to last week's reporting on U.S. Navy movements and actions in the Gulf of Sidra, where journalists seemed comfortable with statements from the Pentagon and White House, the Central American "incursion" was marked by instant doubts.

Some journalists apparently thought the event fulfilled President Reagan's political needs too neatly. With a Senate vote on $100 million in aid to the contras, or counterrevolutionaries, looming, what better wedge than a Sandinista invasion?

Having felt often that they are too easily used by the administration, several members of the news media said they were all the more doubtful of the information that was primarily being fed to them by Reagan spokesman Larry Speakes, who said his numbers on how many Nicaraguans had crossed the Honduran border were "not sanitized before they came to me."

At the same time, remarks by an administration official, later identified by reporters as Speakes, seemed to be accusing the news media of being pro-Sandinista.

"It's unfair, inaccurate and it only serves to lower the level of debate over policy," said Doyle McManus of The Los Angeles Times of Speakes' suggestion that doubters of administration statements were therefore supporters of Nicaragua.

"The main problem was that virtually all the early information was coming from one source and that was the contras themselves," McManus said. "I talked to State, I talked to the Pentagon, I talked to the contras and I realized that the reasons they all matched up so well was that they were all the same version -- it came from the contras."

Several reporters said that by Friday afternoon they believed there had been an "incursion" by Nicaraguans into Honduras. But as the number of Sandinistas seemed to vary from 2,000 to 400 depending on the source, some questioned whether it was the worst invasion to date, as advertised by some administration officials, or a border battle like dozens of others in the last few years.

Reporters also said they are trying to find out whether Sandinista troops were pursuing contras who had attacked Nicaraguans a few days before.

"We're still not certain about some of the details, but the president managed to stampede through $20 million before anybody knew what happened," said Lars-Erik Nelson, Washington bureau chief of the New York Daily News. He referred to the president's decision to give emergency support to Honduras, including $20 million and U.S. helicopters to ferry Honduran troops to their border.

Still, it was Monday that set the tone of confusion about the Central American border fighting, a tone that carried through most of the week.

Dan Rather on the "CBS Evening News," for example, gave a brief report, noting that it came from U.S. intelligence sources. Rather also said that a Honduran official "told CBS News tonight that he knows of no such incursion."

In contrast, ABC correspondent Peter Collins reported that a contra group in Honduras Monday "engaged in the heaviest fighting ever to break out on Honduran territory between the contras and the Sandinistas. As many as 2,000 Sandinista troops have crossed . . . from Nicaragua and penetrated 15 to 20 miles inside Honduras."

For Tuesday's papers, The New York Times held back the story in the first edition because one Times editor said the newspaper had trouble getting "independent" confirmation in Honduras. The Washington Post used a front-page story about the invasion as related by diplomatic sources in Honduras. The Los Angeles Times buried it, and The Baltimore Sun did not publish a report.

By Tuesday, the Hondurans were saying that there had been an invasion and that it was a serious threat to their sovereignty.

Still, there were doubts. On Tuesday night, for example, "CBS Evening News" included an account from Richard Schlesinger in Honduras who said that "one Honduran official told me he plans to go to the beach today and his only worry was whether a cold front that's approaching Honduras will ruin his trip."

Schlesinger also told Rather that one Honduran source saw it as a "propaganda ploy."

"Basically, the problem until [Thursday] was that we couldn't get any independent confirmation," said Warren Hoge, foreign editor of The New York Times. "This is something that has happened out of our sight and that makes it different from things the White House talked about that we can eyeball ourselves. It isn't a matter of being skeptical; it's just a matter of being careful."

Even on Thursday, some of the reporters taken to the border area were being careful to say only what they knew, not what they seemed to know.

A report in The New York Times Friday by James LeMoyne noted that one of five bodies shown to reporters still wore boots that said "Made in Nicaragua" in Spanish. He wrote that they appeared to carry no other identification.

"To me, the confusion about the whole thing is best symbolized by a headline in a Honduran paper Wednesday," said Associated Press reporter George Gedda. "It says, 'Washington Tells Hondurans We Are at War.' "