U.S. Navy officials are assessing the damage after the Ticonderoga-class guided-missile cruiser USS Antietam dumped a significant amount of oil into Tokyo Bay while anchored near Fleet Activities Yokosuka.
The incident was characterized as an engineering incident in a statement by U.S. Pacific Fleet. The Antietam ran aground, a Navy official confirmed to Military.com, though it remains unclear to what extent it grounded or the causes of the incident.
Navy Times, which first described the mishap, reported the Antietam dumped 1,100 gallons of oil as a result of the incident. But Pacific Fleet officials declined to confirm how much oil was discharged, saying an investigation is underway to assess the situation.
Following the mishap, the Antietam was safely returned to Yokosuka with the help of tugs attached to the installation. Navy divers are inspecting the ship to determine damage, Pacific Fleet officials said in a release.
No American sailors or Japanese personnel were injured, officials said.
More information is expected to be made available in coming hours as morning dawns in Japan.
"The Navy is still working to determine the exact location that the spill took place and will take measures to minimize impacts to the environment as appropriate," Lt. Cmdr. Matt Knight, a PACFLEET spokesman, said in a statement. "The Navy is cooperating with the Government of Japan and Japanese Coast Guard in response to this issue."