The U.S. military confirmed that at least two were killed in a crash of a B-52 bomber off Guam on Monday.
According to the military, six vessels, three helicopters, two F-15 fighter jets and a B-52 bomber have been sent to search for four missing crew members in the Pacific Ocean area, a joint operation by the Air Force, Navy, Coast Guard and local police.
The Air Force said that the Louisiana-based B-52 bomber crashed about 48 kilometers northwest of Apra Harbor when it was conducting a flyover in the Liberation Day parade to commemorate the anniversary of the U.S. military's arrival on Guam after it took it over from Japan.
An investigation into the incident would be conducted by a board of officers, it added.
It was the second accident for the U.S. Air Force this year on Guam. A B-2 stealth bomber was down in February shortly after it took off from a Guam air base, leaving a 1.4 billion-dollar loss but two pilots survived.