The US Navy keeps finding traces of jet fuel in the water on the aircraft carrier USS Nimitz, even after it thought the water was safe

• The US Navy recently found traces of jet fuel in the water on board the USS Nimitz aircraft carrier.
• Water testing on Sept. 19 originally didn't reveal any contamination, a Navy official told Insider.

After determining the water on the ship was safe, the US Navy again found traces of jet fuel in the water on board the aircraft carrier USS Nimitz, a Naval Air Forces official confirmed to Insider on Wednesday.

Officials tested samples of the Nimitz's waste water on September 19 following the carrier's arrival at San Diego's Naval Air Station North Island.

Those laboratory tests, which were conducted several days after traces of jet fuel were initially detected in the ship's water, did not reveal any "measurable" amounts of hydrocarbons, highly-combustible jet fuel components, Ensign Bryan Blair, a Navy spokesperson, told Insider.

But testing of water samples from the Nimitz's potable water tanks on September 21 — just two days later — did yield "detectable traces" of hydrocarbons, Blair said. The Nimitz's departure from San Diego has since been postponed so officials can continue to test and evaluate the ship's water.

"The health and wellbeing of our Sailors is a top priority, and the internal potable water system remains offline until we are certain it can produce the highest quality water for the crew," Blair said. Since September 17, he added, the Nimitz has been connected to San Diego's water supply, which "continues to provide fresh water to the crew that has been tested safe for use."

Navy Times reported that traces of jet fuel — also known as jet propellant-5 or simply JP-5— was originally found in the Nimitz's water system on September 16 while the ship was in the Pacific Ocean. USS Nimitz Spokesman Lt. Cmdr. Adam Demeter told Task & Purpose that the crew "immediately took action," a response that preceded the September 19 testing.

It was not immediately clear how many individuals, if any, may have been impacted by the contaminated water.

According to a USNI News report, it is possible for drinking water can become contaminated with jet propellant-5 because the two mix in a ballast tank system used by the Nimitz. A ship's ballast tank system helps control its buoyancy and stability.

The USS Nimitz was built by Newport News Shipbuilding and commissioned in 1975. The first-in-class ship was the second nuclear-powered aircraft carrier built after the USS Enterprise, a carrier known as the "Big E" that has been decommissioned and is awaiting scrapping. The 1,092-foot-long Nimitz, which can carry dozens of aircraft and thousands of personnel, is slated to be decommissioned in 2025.