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A spooky SOS call from on board a ship where the entire crew was found dead and 'frozen in fear' has been revealed in a chilling secret memo as the maritime mystery continues to baffle the world.

The entire crew of the SS Ourang Medan and its captain were found strewn around the ship with expressions of "convulsive horror" but no obvious injuries that could have killed them.

Before investigations could determine what happened, a fire broke out and the vessel sunk without trace, reports the Sun.

A secret CIA memo detailed the eerie "frenzied" SOS call from on board.

"All officers, including captain dead, lying in chartroom and on bridge... probably whole crew dead," the call said.

Written by C.H Marck Jr, assistant to the Director of the CIA Allen Dulles, in 1959, to an unknown recipient, the memo continues: "There followed a series of indecipherable dots and dashes and then came quite clearly: "I die"."

The document reveals that the agency believed the doomed boat could hold the key to a series of other disappearances in one of the world's busiest shipping lanes.

It was penned years after the dutch vessel is said to have sent a distress call in 1948 while sailing the Strait of Malacca - where Malaysia Airlines flight MH370 vanished in 2014.

The distressing Morse code SOS call, made by a signaller on board SS Ourang Medan, was heard by the crew of nearby ship the Silver Star.

Rescue ships rushed to find the stricken vessel, finding her just 50 miles from the position given.

But investigators "found an eerie sight" when they boarded, the memo continues.

"There wasn't a living creature on the ship," it said.

"The captain lay dead on the bridge. The bodies of the other officers sprawled in the wheelhouse, chartroom and wardroom.

"The faithful 'sparks' was slumped in a chair in the radio shack, his hand still on the sending key.

"The bodies of the crew lay everywhere, in the rooms, in the passageways, on the decks.

"And on all the dead faces was a look of convulsive horror."

Referencing a report by Merchant Marine Council, C.H Marck Jr added that their frozen faces were upturned to the sun with mouths open and staring eyes.

The ship's dog, a small terrier, was also dead with its teeth bared 'in anger or agony'.

The boarding parties decided to tow the vessel to port to continue investigations, but, according to the memo, "at that very moment smoke and flames belched forth" from the hold.

They abandoned the ship and there was an explosion, before it sunk without trace with all the dead crew, never to be seen again.

Strangely, the coast guard didn't report it until 1954 - six years after it sank.

Some question if it ever existed, with no mention in the Lloyds List of shipping and no record of the Silver Star attempting a rescue.

Conspiracy theorists question if several countries worked together to cover the mysterious incident up, while others believe a noxious gas bubbled from the seabed.

The secret CIA document, released to the public in 2013, questioned whether an unknown entity was to blame.

"I feel sure that the SS Ourang Medan holds the answer to many of these aeroplane accidents and unsolved mysteries of the sea," the author wrote, pondering the mysteries of the stretch of sea home to many shipwrecks.