The Los Alamos Scientific Laboratory in New Mexico barred the public from its library yesterday to stop a researcher from examining unclassified documents on open shelves. The researcher is aiding the Progressive magazine's legal fight to print an article on the H bomb Department of Energy spokesman James Bishop said here that "inadvertently, some classified material" had gotten into the library's public document room. He said the closing will enable the laboratory staff to determine "whether any other similar mistakes have occurred."

The facility will reopened after the review is complete, Bishop said.

In New York City, the American Civil Liberties editors Erwin Knoll and Samuel H. Day Jr., denounced the action as an "outrage." It is "an incredible infringement of our ability to try this case," said ACLU national staff counsel Charles S. Sims.

The researcher, Dimitri Rotow, 23, of Alexandria, who is on leave from undergraduate studies at Harvard, is regarded by some as a genius. Last year, he told a Senate hearing that, using only publicly available information, he had designed a series of nuclear weapons. Experts at the hearing indicate the designs were workable.

The Progressive article, written by Howard Morland, also is said by the magazine to be based entirely on information available to anyone. In March, however, a federal judge in Milwaukee issued a preliminary injunction requested by the government to stop publication. The magazine is appealing the ruling.

The ACLU retained Rotow to go to the Los Alamos document room and look for unclassified materials to bolster the magazine's case. Accompanied by an aide, he started work last Monday, introducing himself again to library staff members who had met him when he was preparing his bomb designs.

According to the ACLU's Sims, Rotow departed the library Wednesday night after leaving on a table a document from an open shelf and photocopies he had made of certain pages of the document, which bore no classification stamps.

Upon returning the next morning, Rotow found the document and the copies missing from the table. The document was not on the shelf, and the index card for it had been removed from the catalogue.

Late Thursday, officials told Rotow that the library had been placed "in a classified mode," Sims said. Then, after giving what Rotow and Sims regarded as vague, unpersuasive and conflicting explanations, officials told Rotow yesterday that the library, except for the card catalogue, would be shut down indefinitely.

In a conservation with Sims, Charles I. Brown, the laboratory's associate director for administration, said the library staff had found "an aberration in the declassification procedure."

Brown also told Sims, a library spokesman confirmed, that the library will inventory all materials in the declassified section, a task expected to take at least two weeks.

Meanwhile, Brown said, Rotow, using the card catalogue, will be allowed to request whatever materials he wants. These then will be screened to be sure none should be classified, Brown said.

"Brown said he was doing us a favor by allowing him to use the library under these conditions," Sims said. "He kept saying, 'We're doing you a favor.'"

Asked to identify the document that had triggered the closing, DOE's Bishop said it was part of a quarterly report from the Lawrence Livermore Laboratories in California "that contained a lot of classified material that shouldn't have been there."

The library was closed "in consultation with" DOE's assistant secretary for defense programs, but the decision was made in Los Alamos, not here, Bishop said.

A Justice Department official said, "We don't know what the facts are. We have not had any involvement in this particular incident at all."