Robin GibbRobin Gibb has postponed a series of South American shows after he was taken to the hospital on April 3 with stomach pains, the AP reports.

The Bee Gees singer was supposed to leave for Brazil that day, but doctors advised him not to travel while they identify the ailment. "We are not sure what's wrong with him at this stage and are worried," his spokesman told the BBC.

Not only did he cancel the shows, but Gibb also had to postpone a meeting with Brazilian President Dilm Rouseff. "Robin apologises to all his fans in South America and to all the people who had worked on making this tour possible especially Web Rockers, Midia Digital Ltda and Poladian Productions," said a statement on his website. "Robin was looking forward to meeting and performing for his South American fans."