Relatives of two people killed when a Japanese fishing boat was sunk when it was struck by a U.S. Navy submarine nearly three years ago have asked U.S. transportation authorities to investigate the collision, their lawyer said Wednesday.

Nine of the 35 Japanese high-school students, teachers and crew members aboard the Ehime Maru died when the surfacing USS Greeneville rammed the fishery training vessel off Oahu on Feb. 9, 2001. The accident sparked outrage in Japan and the victims' next of kin later agreed to a compensation settlement with the U.S. Navy.

On Tuesday, the relatives sent a letter asking the National Transportation Safety Board, which investigates crashes in the United States, to scrutinize the Pentagon's program of allowing civilians on board military equipment, said Makoto Toyoda, a lawyer representing the families.