Independent counsel Lawrence E. Walsh has asked about 20 present and former Justice Department officials, including Attorney General Edwin Meese III and former FBI director William H. Webster, to turn over a wide range of documents relating to the department's controversial inquiry into the Iran-contra affair last fall.

Informed sources said the request also covers documents related to earlier probes by the Justice Department and the Federal Bureau of Investigation into allegations of gun smuggling on behalf of rebel forces in Nicaragua as well as violations of the Neutrality Act.

"It's just incredible," one official said of the document list that Walsh and his prosecutors submitted early this month. "They asked for the kitchen sink of everybody."

Sources said the request did not represent an expansion of Walsh's inquiry but rather an effort by his prosecutors to ensure that nothing had been overlooked before former White House aides Oliver L. North and John M. Poindexter began testifying under grants of limited immunity from prosecution.

Walsh cannot use testimony that Marine Lt. Col. North and Rear Adm. Poindexter gave on Capitol Hill or any documents or other information that might have come to light as a result of that testimony. As a result, the sources said, the independent counsel wanted to ensure that he had requested every potentially useful scrap of information from the Justice Department before the two men made their appearances.

In fact, sources said, most of the materials had already been turned over to Walsh's investigators. Compliance with the request, they said, was mainly a matter of identifying and finding the items still outstanding -- from personal notes and appointment calendars to telephone messages and routing slips.

According to the sources, a major part of Walsh's investigation has been spent in determining whether attempts last fall to cover up the administration's secret arms sales to Iran represented obstruction of justice. As part of that effort, the special prosecutors have also been trying to find out whether the so-called fact-finding inquiry Meese conducted last Nov. 21-25 facilitated the cover-up and prompted North and others to engage in last-minute shredding of evidence.

North told the House-Senate Iran-contra committees at one point that he shredded some documents last Nov. 22 while Meese's deputies were in an adjacent room. The FBI did not begin its criminal investigation until Nov. 26, after Meese had publicly announced the diversion of some profits from Iran arms sales to aid the contras.

Walsh's comprehensive request for information, the sources said, covered the entire Justice Department, including the FBI. But it also specified about 20 officials by name -- including Meese, Webster, who is now director of central intelligence, and Oliver B. Revell, a top FBI official who had frequent dealings with North. The first batch of documents, the sources added, was due July 13 and the remainder is due next Monday.