Actress Carrie Fisher suffers heart problem on flight and is in the ICU.

LOS ANGELES (Reuters) Actress and writer Carrie Fisher, best known for her role as Princess Leia in the "Star Wars" film series, suffered a heart problem on Friday during a flight from London to Los Angeles and was rushed to the hospital, where she remains in the intensive care unit (ICU).

According to Todd Fisher, the actress's younger brother, Carrie is in critical condition. He also stated that she remains under medical treatment in the ICU of a Los Angeles hospital several hours after falling ill.

"It's not reasonable to say 'stable.' I'm not saying she's doing well or that she's not doing well," he told Reuters by telephone when asked about his sister's health. "She's in the ICU," he added.

Todd Fisher did not provide details about his sister's condition or the circumstances of the incident on the plane. He said he received the information from Carrie's assistant.

The Los Angeles Times reported that the actress had become very ill on the flight, which landed at Los Angeles International Airport the previous day, citing an unnamed source.

According to celebrity news website TMZ.com, Fisher suffered a "severe heart attack" 15 minutes before landing, and an emergency medical aide who was on board was brought into the first-class cabin to provide assistance.

The city's fire department confirmed that it had dispatched personnel to an arriving flight at the airport to treat a patient in "cardiac arrest," but did not provide any identification, citing confidentiality laws.

Two passengers who said they were on board the flight and seated near Fisher posted messages on Twitter reporting that she had become ill.

United Airlines issued a statement saying that a medical team went to meet flight 935 from London to Los Angeles after the crew reported that a passenger was "unresponsive," but the airline did not name the passenger in question.

(Reporting by Steve Gorman and Alex Dobuzinskis)