Todd Fisher told The Associated Press on Friday night that his sister was receiving excellent care, but said that he could not classify her condition. He had earlier told the AP that she had been stabilized and was out of the emergency room.
In a subsequent interview he said many details about her condition or what caused the medical emergency are unknown, and much of what had been reported was speculation.
"We have to wait and be patient," he said. "We have so little information ourselves."
Carrie Fisher, 60, experienced medical trouble during a flight from London and was treated by paramedics immediately after the plane landed in Los Angeles, according to reports citing unnamed sources.
Celebrity website TMZ, which first reported the incident, said anonymous sources told them the actress suffered a heart attack.
Fisher's publicists and representatives for her mother, Debbie Reynolds, and her daughter, Billie Lourd, did not immediately return calls from the AP.
Los Angeles Fire Department spokesman Erik Scott said paramedics administered advanced life-saving care to a patient at Los Angeles International Airport on Friday and transported the person to a nearby hospital. He did not identify the patient.
A large gathering of reporters was camped outside Ronald Reagan UCLA Medical Center in Los Angeles hospital, where TMZ and the Los Angeles Times reported she had been taken.
Fisher is considered by many to be a member of Hollywood royalty — her parents are Reynolds and the late singer Eddie Fisher.
Catapulted to stardom when the original "Star Wars" was released in 1977, Fisher reprised the role as the leader of a galactic rebellion in three sequels, including last year's "Star Wars: The Force Awakens."
The author and actress may be best known for her portrayal of Leia, but she is also an accomplished writer known for no-holds-barred accounts of her struggles with addiction and mental illness.
Her thinly veiled autobiography "Postcards from the Edge" was adapted into a 1990 film version starring Shirley MacLaine and Meryl Streep. She also transformed her one-woman show "Wishful Drinking," which played on Broadway and was filmed for HBO, into a book.
Most recently, Fisher has been promoting her latest book, "The Princess Diarist," in which she reveals that she and co-star Harrison Ford had an affair on the set of "Star Wars."