Eight people have been rescued since a United States Navy aircraft with 11 crew and passengers on board crashed into the Pacific Ocean on Wednesday afternoon, the US Navy said. It was on its way to the aircraft carrier USS Ronald Reagan in the Philippine Sea.

The Japan-based 7th Fleet said the aircraft crashed southeast of Japan’s Okinawa, and a search and rescue operation has been on since. The cause of the crash is not known yet, and the names of those on board are being withheld as the next of kin are being notified, the US Navy said.

“Personnel recovery is under way, and their condition will be evaluated by USS Ronald Reagan medical staff,” the Navy said earlier.

The 7th Fleet has had two fatal accidents in Asian waters this year, leaving 17 sailors dead, AP reported. Eight top Navy officers have been removed from their posts, including the commander of the 7th Fleet.

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

The Navy has concluded the collisions were avoidable and resulted from failures by crew and commanders, the AP report said.