Briton Eddie Irvine pulled out of the Austrian Grand Prix on Friday evening after suffering abdominal pains which first reports suggested were due to appendicitis.
The Jaguar driver, who won last year's race but ended the opening practice session in 21st place, had felt unwell since arriving at the circuit on Thursday and was advised to pull out by surgeons at the A-1 Ring's Medical Centre.
"Having taken the advice of the surgeons here in Austria, Eddie has flown back to England to undergo further tests so a fuller diagnosis can be given," said Neil Ressler, Jaguar's chairman.
"It was the opinion of the medical team that given the discomfort he was in there was little point in him continuing this weekend. Our priority is to ensure that Eddie returns to full health as quickly as possible."
Brazilian Luciano Burti, who is Jaguar's official test driver, will take Irvine's place for Sunday's race.