In keeping with the agency’s strict medical privacy policy, NASA officials have not identified the astronaut in question or provided any details about the nature of the medical issue.

A Crew Dragon capsule ferried four astronauts into space Sunday night after a rumbling departure from the Kennedy Space Center in Florida, setting off on a 27-hour pursuit of the International Space Station on SpaceX’s first operational crew rotation flight to the orbiting outpost.

A Russian Progress cargo craft re-entered Earth’s atmosphere over the South Pacific Ocean early Friday after spinning out of control following liftoff April 28 with supplies for the International Space Station.