The fishing boat, Jeneatte, which caught fire on Wednesday at the main dock in American Samoa, sunk on Friday about 17 miles south of Tutuila.
All that was saved from the boat before it went down was its skiff.
The purse seiner had a full load of fish on board as it had not unloaded its catch when the fire started.
Investigators from the US Coast Guard in Hawaii arrived on Friday to look into the fire.