Senate Ethics Committee Chairman Adlai E.Stevenson (DIII.) said yesterday he can no longer make the assertion he offered two weeks ago that no member of the Senate is involved in the South Korean influence-buying scandal.

Stevenson said he changed his position after reviewing documents obtained by Justice Department investigators probing the activities of South Korean businessman Tongsun Park.

But Stevenson, spaking at a Chicago news conference, refused to comment when asked specifically if the documents contain the names of any senators.

Because of the mounting evidence being accumulated by the Senate Ethics Committee, the committee may need for an independent investigation of South Korean efforts to gain influence in the Senate, Stevenson said.

A House committee has been pursuing a full-scale investigation of House members who received gifts and cash from various South Korean operatives over the past 10 years.

A shower of leaks from that investigation has indicated that 20 or more House members may have received South Korean gifts or money in violation of statutes or House rules. Most reports on the scandal to date have made no mention of the Senate.

But Stevenson and Sen.Harrison Schmitt (R.N.M.) ranking Republican on the Ethics Committee, began a "quiet. informal" inquiry this spring into possible Senate connections.

Asked about the inquiry two weeks ago, both men said no current Senate members appeared to be involved.

Since then the committee has met with CIA Director Stansfield Turner and Attorney General Griffin B.Bell to review investigative records on the case.

Those reviews, Stevenson said yesterday, forced him to take back his earlier assurances that there was no Senate involvement.

Committee sources say Bell showed the senators a list compiled by Jay Shin Ryu, a former aide to Tongsun Park. Park is alleged to have been at the center of the influence buying.

The Ryu list reportedly contains about two dozen names and dollar figures that seem to show how much money each person listed received from Park. Some who have seen the list say the names are mostly those of House members, but that senators and executive branch officials are also listed.

At a meeting of the Senate Ethics COmmitte last Thursday. Stevenson and Schmitt were authorized to look for an outside counsel who would review the extent of Senate involvement in the Korean matter.

Stevenson said yesterday he hoped to retain a counsel within a week or two. Stevenson's office said the new counsel would work on the Korean probe "for the most part." but would also handle other, unrelated committee business.

At the press conference at the American Bar Association convention in Chicago, Bell said again that Park, who is now in London and has refused to cooperate with investigators, is the key to the probe.

Without testimony fromPark, Bell said, the Justice Department could probably expect indictments only on income tax charges in the case-not on more serious charges such as bribery or defrauding the U.S. government.