A statement on the health of five-time major champion Seve Ballesteros is expected over the weekend, with further tests planned on the 51-year-old today.
The Spaniard fainted on Monday and has remained in intensive care while tests have been carried out.
He claimed to be feeling fine on his website on Thursday and thanked well-wishers for their support, but a statement confirming a serious illness is expected.
Ballesteros remained in a stable condition in Madrid's La Paz hospital yesterday after moving out of the intensive care unit.
Doctors discovered an irregular heartbeat when Ballesteros was admitted to hospital last year, although it is not known if this condition is linked to his current problem.
Ballesteros, who retired from competition in 2007, won The Open three times and the Masters twice.
He won 50 European Tour events and captained Europe to Ryder Cup victory at Valderrama in 1997.