NEW YORK — Lindsay Lohan was to have surgery to remove her appendix, her publicist, Leslie Sloane Zelnik, said Thursday.

Zelnik declined to give details. In response to a query by The Associated Press, Zelnik said in an e-mail that the 20-year-old actress was "having her appendix removed. She is resting comfortably."

Celebrity Web site TMZ reported Zelnik as saying Lohan wasn't feeling well Wednesday and had gone to a doctor, who performed several tests and determined that she was suffering from appendicitis.

Doctors asked her to return to the hospital Thursday to remove her appendix as a precaution, TMZ said.

Lohan, whose screen credits include "Bobby," "A Prairie Home Companion" and "Freaky Friday," was treated for several hours at a Los Angeles area hospital last July for overheating and dehydration after being overcome by the heat on the set of "Georgia Rule."

She was treated at hospitals twice in January 2006 -- in London for a cut on her leg and in the Miami area for an asthma attack. In 2005, she was hospitalized for exhaustion and lost a noticeable amount of weight.