USS Mount Hood, a 13910-ton ammunition ship, was
built at Wilmington, North Carolina, and converted for
Naval service at Norfolk, Virginia. Commissioned in
July 1944, she transited the Panama Canal in August
and was assigned to the South Pacific area to provide
ammunition to the fighting forces. On the morning of
10 November 1944, while she was moored at the
Manus Naval Base, Admiralty Islands, Mount Hood's
cargo of explosives detonated in a massive blast.
The ship was utterly destroyed by the accident, which
killed all those on board her. Damage and casualties
were also inflicted on ships anchored as far as 2000
yards away. Personnel casualties on Mount Hood
and on other vessels totalled 45 known dead, 327
missing and 371 injured.

And didn't a Japanese Battleship suddenly explode one day
during the war?
EDIT: The Jap BBs name was the IJN Mutsu. She blew up on:
http://www.combinedfleet.com/Mutsu.html
8 June 1943:
The MUTSU is moored at the flagship buoy midway
between Hashirajima and the Suo-Oshima islands about
two miles SW of Hashirajima. She hosts 113 flying cadets
and 40 instructors of the Tsuchiura Naval Air Group who
are aboard for a familiarization tour.
Captain Tsuruoka's FUSO is moored about 1,100 yards
SW of the MUTSU. DesRon 11’s flagship, the light cruiser
TATSUTA and several of the squadron’s newly commissioned
destroyers are moored more distantly south of Hashirajima.
1145: After lunch, the MUTSU’s deck crew prepares to move
to mooring buoy No. 2 because the NAGATO is expected to
return at about 1300 from Kure after being drydocked.
There is heavy fog and visibility is down to 500 yards.
The MUTSU's magazines contain a full load of ammunition
including 16.1-inch Type 3 "Sanshikidan" incendiary shells designed as anti-aircraft rounds. Each shell weighs
2,064-lbs. and contains 1,200 submunitions. Each
turret magazine contains 240 shells (120 per gun),
including 50 "sanshiki-dans."
1213: Suddenly, the MUTSU’s No. 3 turret’s magazine
explodes. Vice Admiral Shimizu, Commander of the
First Fleet, a few miles away aboard the NAGATO sees
a brilliant white explosion. Shortly thereafter, he
receives a coded message from the FUSO’s Captain Tsuruoka.
It says: "The MUTSU blew up!"
Sunk: The MUTSU breaks in two. The 535-ft forward
section collapses to starboard, sinks quickly and lies on
the pagoda mast on the floor of the bay. The 147-ft stern
section upends, but remains floating.
The FUSO immediately launches two of her Vedette boats.
Her crew rescues 353 survivors of the 1,474 crewmembers
aboard the MUTSU. Only 13 of the visiting flying cadets/instructors
are among the survivors. The IJN can ill-afford the loss of
140 instructors and pilot trainees, particularly after the
heavy losses sustained in April in Operation "I-Go" during
the reinforcement of the 11th Air Fleet at Rabaul.



