MOL Ship Management (Singapore) said initial reports from the local salvage said that the Felicity Ace had sank around 9am having suffered a list to starboard. The ship is reported to have 220 nm from the Azores.
The ship manager said salvage craft were monitoring the situation.
Fire erupted onboard the 2005-built Felicity Ace on 16 February offshore Portugal and all 22 crew were safely evacuated.
Salvors successfully attached a tow line to the stricken vessel on 25 February.
The vessel was reported to be carrying 3,965 vehicles of the Volkswagen, Porsche, Audi, and Lamborghini brands. Some 1,100 of the vehicles were from Porsche. The cargo was estimated at $401m in value by risk analyst Russell Group.