CONCORD, N.H. >> The remains of 21 sailors killed in the attack on Pearl Harbor and buried as unknowns should be identified and returned to their families, a group of U.S. senators said Thursday.

The sailors were aboard the battleship USS Oklahoma when it was attacked on Dec. 7, 1941, ripped open by as many as nine torpedoes. The ship quickly rolled and came to rest just 20 minutes after being hit. Nearly 430 men died.

The remains of 27 sailors were classified as unknown and buried in the National Memorial Cemetery of the Pacific, known as The Punchbowl, in Honolulu.

In 2003, historian Ray Emory of the Pearl Harbor Survivors Association used military records and personnel files to tentatively identify the 27 men. Five were then definitively identified by the Central Identification Laboratory of the Joint POW/MIA Accounting Command and their remains returned to their families.

Emory also tracked down family members of 21 of the remaining 22 sailors. In a letter sent Thursday to Defense Secretary Chuck Hagel, the group of 15 senators asked that those remains — which are in five caskets — be exhumed and sent to the JPAC lab for identification.

“These families have sought our assistance in the effort to have the bodies of their loved ones exhumed so they can receive a proper burial in their community or be buried in a marked grave in Hawaii,” the senators wrote.

The effort is led by Sens. Kelly Ayotte of New Hampshire and Chris Murphy of Connecticut.