THIS TOWN CONTINUES of buzz with allegations that the South Korean government has spent hundreds of dollars in an effort to buy influence in the U.S. Congress. How many of them are true and how many congressmen are involved are still unanswered questions. As long as they remain unanswered, they will be a cloud over both Congress and American-Korean relations. So it is vital that the executive and legislative branches of our government move as quickly as they can to deal with these allegations.

Despite the need for speed, however, the goal of these investigations must be to get at the pertinent facts - all of them. It would be grevious mistake for the Department of Justice to cut short is investigation simply to bring the matter to an early conclusion and to spare fellow Democrats distress, as some commentators have charged it intends to do. While some statements by Attorney General Griffin Bell may be subject to that interpretation, we do not understand them that way. We read what Mr. Bell has said as promising a full but quick investigation, not a quick but imcomplete one. Surely he recognizes that the last thing this administration - and this country - needs is something that appears to be another coverup.

It is important to keep in mind that the Department of Justice is looking for violations of the criminal law, not just instances of misconduct. Its eventual decision to seek or not seek indictments will notconclude the matter. Prosecutors are in no position to either charge or clear members of Congress for doing things that are wrong but fall short, for substantive or technical reasons, of being indictable crimes. That is the task of Congress itself.

Fortunately, the Congress now seems inclined to act. The ethics committee, armed with a House mandate and a budget of $530,000, has begun investigating whether members received "anything of value, directly of indirectly," from Seoul. The (12 person) committee, not perviously noted for being a tiger, has five new independent-minded members whose presence provides grounds for some confidence in its work.

Meanwhile, Rep. Don Fraser's International Relations subcommittee is today seeking from the Administration Committee a budget of $350,000 for an indepth study of the conduct of recent U.S. Korean relations. This separate investigation would look at allegations military-contract and business corruption, of KCIA misdeeds in the United States, and the like; it would try to see whether and when the State Department and CIA learned of these allegations, and what they did about them. Rep. Edward Derwinsi for one, a self-styled hardliner who feels the inquiry would damage American-Korean relations, is protesting against its costs as well as its thrust. It seems to us, however, that Mr. Fraser promises an inquiry of substantial value in illuminating the actual texture of relations between the United States and a certain sort of dependent ally. We think his study could produce valuable policy guidelines and we support its full funding. To call it "redundant" as Rep. Derwinski has done, and then keep it going with only half as much money as it thinks it needs, is no sloution.

We add a footnote: The vote in the House for the ethics investigation was 388 to 0: no one dared vote against it for fear of being accused of being on the take. The stink arising from U.S. Korean relations now makes is virtually impossible to obtain a congressional vote on Korea on the merits. It took courage for Mr. Derwinski, who denies any taint and who has been accused of none, to take the position he has. But it is precisely the need to restore an atmosphere in which questions touching Korea can be addressed without prejudice that makes it essential for the cloud over American-Korean relations to be removed.