Chi-Chi's Inc. of Louisville says a Washington investor group is still interested in acquiring the chain of Mexican restaurants.

Hal W. Smith, Chi-Chi's chairman, said last Thursday that The Carlyle Group, which already owns more than 5 percent of the chain's stock, has indicated it is still "interested in discussing some form of acquisition."

Carlyle is a new Washington merchant banking firm headed by executives David M. Rubinstein, a former partner in the law firm Shaw, Pittman, Potts and Trowbridge; William E. Conway Jr., the former chief financial officer of MCI Communications Corp; Stephen L. Norris and Daniel A. D'Aniello, two former Marriott Corp. executives, and former New York buyout specialist Greg A. Rosenbaum.

Carlyle is expected to file documents with the Securities and Exchange Commission today disclosing ownership of more than 5 percent of Chi-Chi's stock.

Last week's disclosure came as Chi-Chi's announced an expanded program to buy back its outstanding shares, a move that might make a hostile takeover more difficult.

On the other hand, if Carlyle holds onto its stock as Chi-Chi's buys back shares, Carlyle's percentage stake in the company should increase. Carlyle rejected an overture by Chi-Chi's to sell its shares back to the company, sources said.

Chi-Chi's said its directors approved an increase in the buy-back plan to 25 percent of its approximately 27 million outstanding shares. Chi-Chi's previously purchased 925,000 shares.

"This program will not effect Chi-Chi's ability to grow and develop the business and will help maximize for the shareholders the cash assets we currently hold," Smith said.

Carlyle Group is represented in the deal by the investment banking firm Drexel Burnham Lambert Inc. Chi-Chi's has been purchasing shares through First Boston Corp.

Carlyle earlier presented a takeover bid to Chi-Chi's in writing, which expired before it was considered, sources said. The Carlyle bid consisted of a mixture of cash and securities.