NEW YORK (AP) _ Former President Clinton remained in a hospital Sunday while recovering from an operation to remove scar tissue and fluid that developed after his heart bypass surgery six months ago, his spokesman said.

``To the best of my knowledge, he continues to recuperate at the hospital,'' spokesman Jim Kennedy said in an e-mail to The Associated Press.

Kennedy said he had no information regarding when the 42nd president might be released.

Clinton, who had the operation Thursday, was expected to spend three to 10 days in New York-Presbyterian Hospital/Columbia University Medical Center.

Doctors described the operation as a low-risk procedure to relieve a problem that crops up in only a fraction of 1 percent of bypass cases. They said the combination of fluid and scar tissue had reduced Clinton's left lung capacity by 25 percent.

Surgeons removed a rind of scar tissue nearly a third of an inch thick in some places.

The former president first noticed the problem when he suffered shortness of breath during his daily four-mile walk near his home in Chappaqua, N.Y., about 40 miles north of Manhattan.