The Justice Department has ended its investigation of an Alexandria-based gun-lobbying group over use the Great Seal of the United States and has begun studying the use of a similiar emblem by another Virginia group.

The U.S. attorney's office in Alexandria said in a letter made public yesterday that the Gun Owners of America and its executive director, former Fairfax County legislator Lawrence Pratt, agreed earlier this month to halt use of the seal on its fund-raising letters.

Separately, the American Security Council, a think-tank near Culpeper, Va., devoted to national security and defense issues, said it has received inquiries from Justice about a computerized mailing by an affiliated organization, the United States Congressional Advisory Board.

The fund-raising letter, which council president John M. Fisher said has yielded at least $700,000, carries the names of Sens. Paul Laxalt (R-Nev.) and Dennis DeConcini (D-Ariz.) and Reps. Jack Kemp (R-N.Y.) and Bill Chappell Jr. (D-Fla.) as cochairmen, as well as an eagle insignia clutching olive branches and arrows.

Fisher described the insignia as "deliberately different" from the Great Seal and said Justice's inquiry has been referred to the council lawyers.

The initial investigation grew out of complaints from constituents of Rep. G. William Whitehurst, a Virginia Beach Republican. Federal law bars use of the seal by private groups.