Crew members on a Greek product tanker boarded by pirates in the Gulf of Guinea are said to be safe in the vessel's citadel.
Security company Dryad Global told TradeWinds the seafarers remained mustered in the safe room on board the 10,700-dwt Maria E (built 2007) on Wednesday.
The vessel is adrift about 40 nautical miles (74 km) northwest of Sao Tome island.
The tanker was boarded on Tuesday by a gang of gunmen operating from a Chinese tuna boat seized at the weekend and used as a mothership.
The criminals are also thought to be behind attacks on a Teekay LNG Partners-owned LNG carrier, a Thenamaris VLCC and a product tanker since Monday.
Mothership moves away
Dryad said the fishing vessel, Lianpengyu 809, left the waters around the Maria E on Tuesday afternoon, heading north-east towards Nigeria.
The vessel has been tracked 78 nautical miles south of Brass.
Dryad told TradeWinds it is "highly likely that the pirates will abandon her offshore and kidnap some or all of her crew".
The Maria E was targeted 108 nautical miles off Sao Tome island.
Diaplous Maritime Services reported on Tuesday evening that a military ship was underway to meet the tanker.
The Maria E is operated by Lotus Shipping of Greece, which has not commented on the situation.
The crew of the fishing boat are understood to be Chinese, Indonesian and Gabonese nationals. Earlier reports said 14 people were on board.
The mothership is described as having a blue hull and a white superstructure.
Dimensions have been given as 41.68 metres long and 7.6 metres wide.
Vessels are being urged to avoid the area, due to a critical risk of further attacks.
