The Justice Department has begun an investigation of an Alexandria-based gun lobbying group's mass mailing that carried a symbol resembling the congressional seal and the words "Official Congressional District Survey."

Deputy Assistant Attorney General Mark M. Richard said this week the department believes the mailing may violate federal law prohibiting misuse of the so-called Great Seal. The case has been sent to the U.S. attorney in Alexandria for possible legal action, Richard said.

Richard's comments were contained in a letter to Rep. G. William Whitehurst, a Virginia Beach Republican. Whitehurst requested the investigation in late May after a constituent complained about the group, Gun Owners of America Inc. A fund-raising letter accompanying the opinion survey, addressed to "Dear Fellow Gun Owner," was signed by former Fairfax County delegate Larry Pratt, the organization's executive director.

Pratt did not return several telephone calls from a reporter yesterday.

Survey responses--to such questions as, "Do you believe that registering all of the 50 million handguns in America will significantly reduce the number of murders in our country?"--were to be submitted to members of the Virginia congressional delegation.

The letter urged gun owners to rally against liberals' attempts to ban hand guns. "This liberal 'gun-banning' idea could lead to the nationwide disarmament of law-abiding citizens at the same time that violent crime is increasing," Pratt wrote.

In a May 20 letter to Justice, Whitehurst attacked what he called the mailing's "alarmist language" and "scare tactics." He said he was most concerned by use of the "Great Seal, particularly when it is used to solicit money from my constituents."

Whitehurst opposes confiscation of all handguns, but favors as a "reasonable precautionary measure" a proposed waiting period for would-be gun purchasers to allow time for a check of police records, an aide said yesterday.