It was not immediately clear what caused Sunday’s blaze on the Bonhomme Richard, an amphibious assault ship and light aircraft carrier.
According to Krishna Jackson, a Navy spokeswoman, the ship had been docked for scheduled maintenance between deployments.
She suggested that it was unlikely for a docked ship to normally have large artillery onboard.
There were, meanwhile, indications that the ship could continue burning for days.
When the fire was reported around 8:30 am local time, some 160 sailors were said to be aboard the ship, which normally carries a crew of roughly 1,000.
"Just a lot of shock, just a lot of confusion. You don't know what happened, if there was you know an attack, or there was a mistake on the ship, you don't know," said US Navy veteran Joseph Walton.