Apr 16 UPDATE:
Tanker was located on Apr 14 or 15, reportedly 65 nm SE of Abijan, Ivory Coast, and was taken to Abijan same day. All 20 crew are safe, no kidnappings. Tanker was loaded with unspecified oil product, the main and only aim of hijack, as it came out. Cargo (part of it most probably) was siphoned. So for some 4-5 days tanker was moving around in waters with rather intense traffic, near coastal States inner waters, with ongoing full-scale search operation, and remained unnoticed.

April 11
Merchant ship was attacked in the afternoon Apr 10 in Gulf of Guinea, understood it’s tanker SUCCESS 9. Coordinates and time coincide with attack position and time. AIS off since time of attack, so most probably tanker was boarded by pirates. Awaiting confirmation of tanker ID, and updates.

Source: FleetMon.com