Pirates attacked an oil production vessel off Nigeria in the early hours of Thursday and kidnapped nine Nigerian nationals, the ship’s owner BW Offshore said.

The Sendje Berge ship was undergoing maintenance when the attack happened, BW Offshore’s Chief Financial Officer Staale Andreassen said.

The Oslo-listed company said none of the people remaining on the vessel were injured.

“We are working now with the Nigerian authorities to get those nine people safely back,” Andreassen added.

The vessel, a floating production, storage and offloading vessel (FPSO) that can produce about 50,000 barrels per day, was working at the Okwori oilfield operated by Addax Petroleum, a part of China’s Sinopec Group.

A maritime security firm Dryad Global, citing unidentified reports, said the attack involved three boats and explosives, making it unusual.

Andreassen said he could not confirm that a number of boats had been involved, but denied that explosives were used during the attack.

Reuters