A sailor aboard the nuclear-powered submarine USS Nebraska died Sept. 20.

The Navy recently identified the sailor as Machinist Mate 3rd Class Michael Gentile of Fairfield, Maine.

The Navy submarine was conducting operations near the island of Oahu, Hawaii when the Gentile died, according to a Navy news release. The Navy described the sailor’s death as accidental.

Lt. Kyle Raines said Gentile was given medical treatment on board the submarine and was placed on a medical helicopter. He died while en route to a hospital.

Raines said the accident was “an isolated incident” and no other sailors were injured.

Gentile, 21, joined the Navy in July 2005 and had been assigned to the USS Nebraska since Nov. 15, 2006. He previously served on the USS Alaska.

An investigation into the accident is ongoing and memorial service plans for Gentile are pending.

The USS Nebraska is homeported at Naval Base Kitsap-Bangor.