The Navy yesterday said it continues to investigate the recent death of a 21-year-old sailor who died aboard the ballistic missile submarine USS Nebraska as it operated in the vicinity of Hawai'i.

Machinist's Mate Fireman William Mack was given a full military funeral over the weekend, according to the Chattanooga, Tenn., Times Free Press.

He was buried in Booneville, Tenn. The Navy said Mack was found in the submarine's berthing area on April 19.

"It's a very difficult thing for the crew and certainly for the sailor's family and friends ," said Lt. Cmdr. Dave Benham, a spokesman for the U.S. Pacific Fleet submarine force at Pearl Harbor.

"Anytime we lose a sailor, that affects everyone who he has come into contact with — so we'd like to express our condolences to his family and friends during what is obviously a very difficult time," Benham said.

Agents with the Naval Criminal Investigative Service out of Pearl Harbor were brought out to the submarine following the death, officials said. Benham yesterday said the Navy is waiting on medical reports, including autopsy and toxicology results.

The 560-foot Nebraska, with a crew of about 155, carries MK-48 torpedoes, but it primarily has a role as part of the U.S. nuclear arsenal with 24 Trident II D-5 ballistic missiles tubes.

The U.S. Pacific Fleet submarine force has eight Ohio-class ballistic missile submarines, or "boomers," based out of Bangor, Wash. The Navy said the Nebraska did not stop in Pearl Harbor after the death.

All of the submarines homeported at Pearl Harbor are either Los Angeles- or Virgina-class attack subs that do not carry ballistic missiles.

In September, the Nebraska experienced another death while it operated off Hawai'i. Machinist Mate 3rd Class Michael A. Gentile, 21, was killed on the submarine near O'ahu.

The Naval Safety Center said Gentile died after becoming entangled and pinned in the rudder ram — part of the sub's steering mechanism — during cleaning duty.

The Navy said the crewman was mortally wounded while the ballistic missile submarine was submerged and conducting routine operations.