NASA and the presidential commission studying the loss of the Challenger are investigating an allegation that some space agency officials destroyed documents pertaining to the shuttle's solid rocket boosters despite a directive impounding documents after the Jan. 28 explosion, officials said yesterday.

The allegation, made in an unsigned, handwritten letter to the presidential commission headed by former secretary of state William P. Rogers, is directed at engineers of the Marshall Space Flight Center in Huntsville, Ala. The Marshall center supervises the shuttle's solid rocket booster program. A defective joint in the right booster has been identified as the cause of the accident that killed the seven Challenger astronauts and destroyed the shuttle. A handwritten, unsigned letter containing a similar allegation was recently received by The Washington Post.

It also was learned yesterday that National Aeronautics and Space Administration officials at Marshall have signed a major "recovery" contract with booster manufacturer Morton Thiokol Inc. for the redesign and testing of improved rocket booster joints. The contract is estimated to be worth about $200 million and could mean millions of dollars in new profits for the company at a time Thiokol has come under sharp criticism from Congress over its treatment of two engineers who warned against launching the Challenger and were overruled.

The profit margin for Thiokol on the contract "is a somewhat sensitive issue right now" and has not been resolved, one NASA official said. The contract has not been announced by the space agency.

Officials said, however, because Thiokol is the only manufacturer of solid rocket boosters, the space agency had no choice except to sign a contract with the firm to redesign the booster joints.

Frank LaRocca, counsel to NASA's inspector general, said of the investigation of the document-destruction allegation, "We are pouring our resources into it." Asked how seriously the agency is taking the allegation, he said: "If it was a flight of fancy, I don't think we'd be wasting our time . . . . It's serious enough to warrant our initial attention."

The Marshall center issued a statement yesterday saying that "management is not aware of the destruction of any records associated with the . . . accident, and certainly not any that would have been pertinent to the investigation."

"If that kind of information was in fact destroyed," the statement said, "it was done in violation of center directions and intent."

A Federal Bureau of Investigation agent working for the Rogers commission was in Huntsville yesterday, interviewing officials there under oath about the allegation.

The letter that prompted the investigation into possible destruction of documents mentions destruction of "weekly notes." Two Marshall center officials said yesterday that weekly notes at the facility are routinely discarded.

The officials described the weekly notes as a sort of internal scratch pad for the various divisions at Marshall, in which engineers, scientists and administrators working on related projects exchange information about technical issues, test results, engineering problems, administrative issues, even upcoming scientific conferences.

The notes are widely circulated, the officials said. "They are about pending developments," said one official who asked not to be identified. "They are not file notes; they are routinely destroyed at the end. Some people keep them, some people destroy them, but if the commission is interested in them, they should be on file somewhere here."

"They are not intended as a system of records," said Marshall spokesman Ed Medal. "The information is very preliminary, kind of note kind of stuff, and they are routinely disposed of."

Both officials said they did not think the weekly notes fell within NASA's impoundment order.

Internal NASA documents previously obtained by the presidential commission showed that Marshall officials knew about problems with the shuttle's rocket booster five years before the accident, but failed to correct them.

The one-page letter received by The Post, which LaRocca said sounded similar to that received by the commission, begins, "This letter does not exist."

It then poses six questions, including: "Was O-ring and SRB [solid rocket booster] joint information destroyed after the 51L [Challenger] accident?" and "Why would anyone want to destroy EP25 weekly notes? Are they protecting themselves?" The letter ends: "DIG IN!"

"EP25" is the mail code for the solid motor branch of the structures and propulsion lab at the Marshall center, a facility that helped to design the suspect boosters.

The letter names seven Marshall employes who might "know about this"; those named could either not be reached or declined to comment.

Because the letter uses several abbreviations common only to employes at the center and because it names individuals, "it would lead you to believe it was written by an insider," LaRocca said.

NASA's official statement on the documents investigation said that on Thursday Rogers "informed NASA that the commission had received information alleging that copies of weekly notes in some files . . . were discarded or destroyed following the accident."

The statement said Bill D. Colvin, the NASA inspector general, was investigating the allegations concurrently with the commission "and appropriate action will be taken as soon as the facts are ascertained."

It could not be determined when the commission received the letter. The Post received its version on May 8. That day a source close to the commission said he knew nothing about the letter or the allegation that Marshall engineers may have destroyed documents.

"If they did [destroy documents]," the source said, "they certainly were poor at it. I don't know what they could have destroyed that would have been worse than what was found."

Colvin is conducting a separate investigation into Morton Thiokol's handling of engineers Allan McDonald and Roger Boisjoly, who had warned against launching Challenger on the night before its Jan. 28 flight. The two engineers told the Rogers commission they were reassigned and punished by the company after they first testifed about their objections in February.

A NASA official, who asked not to be identified, said McDonald was one of several "key personnel" identified in Thiokol's contract who cannot be reassigned or fired without consulting with NASA. But, according to the official, there is no record that Thiokol ever consulted NASA before McDonald was transferred from his job as manager of the company's solid rocket booster program to a new post as "director of special projects" with no staff.