The Koreans did a full investigation report
but it is apparently not public.
A one page IMO summary of the report is included in the above link.
It has the following description of the casualty.
After discharging gasoline in one port,
the tanker was making an 11 hour transit to the next port
where the next cargo was to be loaded.
Following the instructions of the charter,
the crew started tank cleaning operations
by fitting a water driven fan to ventilate the tank
with ducting extending to the lower portion of the tank.
Due to the freezing weather the water in the pipes was freezing
making the operation of the fans difficult
and necessitated starting the operation from the after tanks.
After completing the ventilation of the tank
just forward of the slop tanks,
and considering it to be gas free
two crew members entered the tank to remove residual oil.
There was an explosion which tore away bulkheads to adjoining tanks.
One such tank contained A-1 Jet Fuel and kerosene slops
The hull was breached in way of the tanks and the engine room
and the ship flooded rapidly,
developed a starboard list and sank.
The crew escaped by jumping into the sea
and seven were recovered bypassing ships.
Of a crew of 16, 7 survived,
The cause of the ignition was not identified;
however, it could have been a discharge of static electricity
from winter clothing or fromthe ventilation ducting
or an ordinary metal paint can that was used to carry
tools into the tanks coming into contact with metal and causing a spark.
The crew was under pressure to complete the tank cleaning
operation due to the short duration of the transit
to the next port in that given the equipement avialable
and the weather conditions,
there was insufficient time to ventilate and clean
all the the tanks as requested.
Given the type of cargo to be loaded in the next port,
the report disputes the need to clean tanks in this case.