TOKYO — As the bodies of the seven sailors who died aboard the American destroyer Fitzgerald last weekend were flown back to the United States from Japan on Tuesday, multiple investigations of the fatal collision with a container ship began in earnest.

The United States Navy and Coast Guard are investigating, as are the Japanese Coast Guard and the Japan Transport Safety Board, in an effort to determine what caused the deadly crash in a busy sea lane in the middle of the night.

Japanese officials said on Monday that the accident had occurred nearly an hour earlier than previously believed, and on Tuesday the United States Navy appeared to accept the revised timeline. “We’re not disputing what the Japanese Coast Guard is saying” about the timing of the collision, said Cmdr. Bill Clinton, a spokesman for the Seventh Fleet at the American base in Yokosuka, Japan, south of Tokyo.

The ACX Crystal, the 29,000-ton Philippine-registered ship that collided with the Fitzgerald off Japan, docked in Yokohama on Monday so that its cargo of household goods and machine parts could be unloaded.