Attacks on ships are on the rise in West Africa's Gulf of Guinea.
If confirmed, the weekend hijacking would be the second such seizure off Ivory Coast in under three weeks.
Noel Choong, head of the IMB's piracy reports division, said: "The situation in the Gulf of Guinea is bad. There have been three attacks in five days." He said the other incidents were off the coast of Nigeria.
Many gangs in the Gulf of Guinea are offshoots of groups that once operated in Nigeria's oil-rich Niger Delta, and attacks in waters off Nigeria, Togo and Benin have been common for years.
Ivory Coast recorded its first such hijacking last October when suspected Nigerian pirates seized a tanker carrying gasoline near Abidjan's port. The crew was freed.
Gunmen failed to seize a ship anchored off Abidjan's port in December. Last month, pirates took control of a tanker as it waited to unload its cargo at Abidjan's tanker terminal.
Mr Choong said: "It appears the Nigerian pirates are spreading."