The West German magazine Stern filed suit for fraud today against Gerd Heidemann, the reporter who acquired the faked diaries of Adolf Hitler for the newsweekly, claiming he "named as a source for the diaries a man who in all probability does not exist" and "possibly enriched himself" as well.

As Stern reporters fanned out to track down the source of the diaries, historians and experts who encountered similar papers in the past suggested that Heidemann's account of how the 62 volumes supposedly emerged unscathed from a 1945 plane crash in East Germany to wind up in his hands may be part of an elaborate "smokescreen" to conceal the identity of diehard Nazis seeking to rehabilitate Hitler's name.

Heidemann was flown in a private plane from Bavaria to Stern's Hamburg headquarters Friday after official West German archivists pronounced the diaries fakes because the paper, binding and glue had not been produced until years after World War II.

The 51-year-old journalist, who was interrogated until dawn Saturday by Stern editors about the origins of the diaries, has disappeared from public view. Of his present whereabouts, a Stern spokeswoman today would only say that he needed time to rest and reflect in private.

Heidemann has adamantly refused to reveal how he acquired the diaries, even to Stern's management, which reportedly paid more than $3 million for the bogus volumes, because he insisted that lives could be placed in jeopardy.

The Bonn government denied reports that Chancellor Helmut Kohl had ordered West German intelligence services to explore the alleged East German connection to the diaries.

An Interior Ministry spokesman said the government's involvement ended with the forgery findings and added that "it was now entirely in the hands of Stern" to ascertain the source of the hoax.

Stern journalists today apologized to their readers and expressed shame over the way the magazine handled the affair.

An affidavit signed by 200 of 210 editorial staff members said "even if the 'diaries' had been genuine, respect for the victims of Nazi tyranny should have precluded the style of publication that was chosen."

Since Stern unveiled the diaries in a publicity blitz more than two weeks ago, several respected historians have mentioned that they had examined similar material some years ago.

Prof. Eberhard Jaeckel of Stuttgart University said he was shown documents, paintings and a diary volume all supposedly by Hitler. He said he saw them in early 1980 at the apartment of Fritz Stiefel, a local businessman and ardent collector of Nazi-era mementoes.

In a telephone interview, Jaeckel recalled that Stiefel introduced him to Konrad Fischer, a seller of Nazi goods who offered him the chance to buy "an original diary volume from 1935" by Hitler and suggested the possibility of acquiring "many, many more."

Jaeckel, who has compiled a book on Hitler's writings, said he was only interested in assembling documents until 1924 and declined to buy the volume.

British right-wing historian David Irving, now traveling in West Germany, confirmed by telephone that Fischer has operated a shop in Stuttgart selling Third Reich regalia to Nazi-era collectors and historians.

Irving described Fischer as "about 45, bald with a small mustache," who is known by his neighbors under the name of "Konrad Kujau."

Irving, whose benign treatment of Hitler in his books has generated revulsion among scholars but endeared him to a lingering Nazi clique, said he visited Fischer recently but discovered he had dropped out of sight three weeks ago.

Fischer's connection is intriguing because he has often cited high-ranking relatives in East Germany as key sources of access to Nazi documents, paintings and books.

A cousin of Fischer's now living in Munich, Erwin Fischer, is mentioned by Hitler-era scholars as the man who obtained the diaries of Josef Goebbels, the Nazi propaganda chief, which had come from East Germany.

Among those who traded on the furtive market for Hitler goods, rumors have circulated that Hitler papers were spirited out of East Germany by a Fischer family member, a major general in the East German army.

Other speculative accounts have even cited Oskar Fischer, the East German foreign minister, as a powerful relation helpful to the Stuttgart merchant's trade.

Another Nazi-era collector, August Priesack, who has written about Hitler's life as a painter, said that Konrad Fischer has shown him "absolutely genuine material" that came from the Dresden Museum, either stolen or sold through black market channels.

The London Sunday Times reported that Gina Heidemann, in a weekend talk with one of its reporters, hinted that the source of the diaries came from the "highest possible" levels of the East German government.

But today, the newspaper Bild reported that she had recanted her story, saying she made it up. A Stern editor, Gunther Schoenfeld, claimed that "what Mrs. Heidemann said was nonsense."

Nonetheless, there are clear indications that Heidemann, an avid Nazi-era collector himself for many years, knew Fischer and had even told acquaintances about a fellow Hitler aficionado living in southern West Germany who possessed more than 50 notebooks written by the Nazi dictator.

"I'm absolutely convinced that the volume that Fischer showed me was from the Stern collection," recalls Jaeckel, who added that Heidemann was fairly well known as an eager buyer on the Hitler "gray market."

The West German magazine Bunte, a competitor of Stern, said today that in August 1981 Heidemann wrote a letter to Klaus Barbie, the so-called "Butcher of Lyons," who was then in exile in Bolivia, telling him he had "succeeded in securing large parts of Hitler's estate."

In the letter Heidemann mentions that he had acquired "highly interesting drawings, water paintings, boxes of documents and, above all, the Blutfahne" (blood flag)--a reference to a banner carried by Nazis who perished in a 1923 demonstration. Heidemann wanted Barbie to assume custody of the flag, the magazine said.

Jaeckel and Joachim Fest, a noted Hitler biographer, both emphasized that the rumors about Fischer's ties to East German suppliers could easily be a cover for the true authors, who they suspect are part of an old Nazi network.

"One motive of the forger is clear: he was trying to make Hitler look more decent, more humane," said Jaeckel. "He also tended to be favorable to Martin Bormann, but picked on Goebbels and Heinrich Himmler," the head of the SS.

Hans Booms, the president of West Germany's Federal Archives who led the inquiry that proved the diaries were faked, said the forensic studies did not yield clues about the origins but added that "my personal feeling after reading seven volumes is that they came from West Germany."