A number of suspected pirates boarded the Sri Lankan-flagged vessel off the country's northern coast on Monday, residents and officials say.
A spokesperson for the European Union Naval Force, which runs anti-piracy operations in the area, said it was too early to confirm pirate involvement.
If confirmed, it would be the first hijacking of a commercial ship by Somali pirates since 2012.
The EU Naval Force told the BBC: "We became aware of this yesterday evening [Monday], and a light aircraft has been sent at first light today to investigate."
John Steed of the aid group Oceans Beyond Piracy, speaking to Reuters news agency, said, "The ship reported it was being followed by two skiffs yesterday afternoon. Then it disappeared."