Bee Gees singer Robin Gibb has been forced to axe several shows in Brazil after being rushed to hospital with abdominal pains.
The 61-year-old fell ill on Sunday in Britain and was advised by doctors not to travel.
"We are not sure what's wrong with him at this stage and are worried," his spokesman said.
Although they are not sure of the cause, intestinal problems are known to run in the family.
His beloved twin brother Maurice died in 2003 due to complications during surgery to mend a twisted intestine.
And only last year, Robin needed the same emergency surgery which resulted in the singer having part of his intestine removed.
"We don't know if it is a recurrence of the previous problem or if it is something else entirely," his spokesman continued.
Robin had been scheduled to play several concerts across Brazil before he was taken ill.
Photo: © Rex