American star Caeleb Dressel has withdrawn from the rest of the world swimming championships in Budapest.
USA Swimming said on Wednesday that the decision was made "after conferring with Caeleb, his coaches and the medical staff."
Dressel, who had already won two gold medals at the championships, withdrew shortly before Tuesday's semi-finals of the men's 100 freestyle with an unspecified medical condition.
He was also due to race the men's 50 freestyle and 100 butterfly later in the worlds.
"Our priority is and will always be the health of our athletes and we will continue (to) give Caeleb the assistance he needs to recover quickly," USA Swimming said.
The association was to give an update on the swimmer's condition later on Wednesday.
The news followed Australian swimmer Shayna Jack also having to pull out of the rest of the championships after she broke her hand when warming up for the morning's 100-metre freestyle heats.
They are not the only high-profile swimmers to pull out of the competition. Hong Kong's Siobhan Haughey, the Olympic silver medalist in the women's 100, withdrew on Monday due to an ankle injury.
Four-time Olympic medalist Chad Le Clos withdrew from the men's competition on Monday, having revealed on social media that he had been struggling with his breathing for the previous three weeks "since having multiple stints of bronchitis."
Australian Associated Press