A NASA astronaut remained hospitalized Friday evening following the delayed return of a four-person crew from the International Space Station earlier in the morning. 

The crew consisting of NASA astronauts Matthew Dominick, Michael Barratt, and Jeanette Epps, and Roscosmos cosmonaut Alexander Grebenkin splashed down off the coast of Pensacola, Florida, around 3:30 a.m. ET. Friday. 

All four were flown together to Ascension Sacred Heart Pensacola in Florida for medical evaluation following splashdown, and one astronaut still remains, NASA said in a Friday update. 

The remaining astronaut, whom NASA didn’t name, is in stable condition under observation as a precaution due to a "medical issue."

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The crew consisting of NASA astronauts Matthew Dominick, Michael Barratt, and Jeanette Epps, and Roscosmos cosmonaut Alexander Grebenkin splashed down off the coast of Pensacola, Florida, around 3:30 a.m. ET. Friday.  (NASA/Joel Kowsky via AP)

"To protect the crew member’s medical privacy, specific details on the individual’s condition or identity will not be shared," NASA said. 

The other three have returned to NASA's Johnson Space Center in Houston.

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The astronauts’ SpaceX Dragon capsule, which undocked from the space station Wednesday evening, experienced a normal reentry into the Earth’s atmosphere and landing that was "without incident," NASA said. 

This photo provided by NASA shows support teams work around the SpaceX Dragon Endeavour spacecraft shortly after it landed in the Gulf of Mexico off the coast of Pensacola, Florida.  (NASA/Joel Kowsky via AP)

"We’re grateful to Ascension Sacred Heart for its support during this time, and we are proud of our team for its quick action to ensure the safety of our crew members," the agency added. 

The astronauts spent eight months on the space station, two months longer than expected. A normal ISS mission lasts for six months. 

It sometimes takes days or even weeks for astronauts to adjust back to gravity after living on the space station. 

A NASA official told reporters "the crew is doing great" during a Friday press conference after splashdown, without mentioning any medical issues. 

NASA’s Boeing Starliner astronauts Butch Wilmore and Suni Williams will remain at the space station until February after their capsule was deemed too risky to fly them home and returned to Earth last month empty.  (NASA)

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The crew was delayed by both Hurricane Helene and problems with the Boeing Starliner, which eventually returned to Earth last month without its own crew. The Boeing Starliner crew will remain at the space station until February, flying home in a SpaceX capsule that launched last month with two empty seats. 

Originally expected to stay for a week, Wimore and Williams will also remain at the space station for eight months.