A United States Navy aircraft with 11 crew members and passengers on board crashed into the ocean southeast of Okinawa, Japan, on Wednesday, the U.S. 7th Fleet said in a statement.

The aircraft was headed to the USS Ronald Reagan aircraft carrier, which is deployed to the Philippine Sea. A search and rescue operation was launched from the carrier, the Seventh Fleet said. It said later that a search was still underway for three missing personnel, and that eight had been rescued in good condition.

"Our entire focus is on finding all of our Sailors," Rear Adm. Marc H. Dalton, the Commander of the 7th Fleet's Task Force 70 said later in a statement. "U.S. and Japanese ships and aircraft are searching the area of the crash, and we will be relentless in our efforts."

8 personnel recovered following C2-A crash have been transferred to #USSRonaldReagan for medical evaluation and are in good condition. Search and rescue efforts for three personnel continue with @USNavy and #JMSDF ships and aircraft on scene. https://t.co/uuIWd9SUSF pic.twitter.com/rvFC81Qbqq — 7th Fleet (@US7thFleet) November 22, 2017

Japanese Minister of Defence Itsunori Onodera told reporters that U.S. Navy officials had informed him the crash could be the result of engine problems.

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The Reagan was operating in the Philippine Sea during a joint exercise with Japan's Maritime Self-Defense Force when the twin-propeller plane crashed at 2:45 p.m. Japan time. The cause of the crash was not immediately clear and the incident will be investigated, the Navy said.

The @USNavy is conducting search and rescue following aircraft crash. We are monitoring the situation. Prayers for all involved. https://t.co/1AxmegKqvu — Donald J. Trump (@realDonaldTrump) November 22, 2017

President Trump said in a tweet Wednesday morning that he was monitoring the situation.

U.S. and Japanese naval ships and aircraft are searching for the missing. Japan's Defense Ministry said the crash site is about 90 miles northwest of Okinotorishima, a Japanese atoll.

September 2017 file photo shows aircraft carrier U.S.S. Ronald Reagan AP

The names of the crew and passengers are being withheld pending notification of next of kin.

Philippine military spokesman Maj. Gen. Restituto Padilla said his military alerted its ships and aircraft shortly after learning about the crash but could not provide help because of the distance from the country.

The Nov. 16-26 joint exercise in waters off Okinawa has been described by the Navy as the "premier training event" between the U.S. and Japanese navies, designed to increase defensive readiness and interoperability in air and sea operations.

The Navy's Japan-based 7th Fleet has had two fatal accidents in Asian waters this year, leaving 17 sailors dead and prompting the removal of eight top Navy officers from their posts, including the 7th Fleet commander.

The USS John S. McCain and an oil tanker collided near Singapore in August, leaving 10 U.S. sailors dead. Seven sailors died in June when the USS Fitzgerald and a container ship collided off Japan.

The Navy has concluded that the collisions were avoidable and resulted from widespread failures by the crews and commanders, who didn't quickly recognize and respond to unfolding emergencies. A Navy report recommended numerous changes to address the problems, ranging from improved training to increasing sleep and stress management for sailors.