Abuja, Nigeria ? Gunmen in speedboats raided a Norwegian vessel conducting seismic surveys off Nigeria’s oil-rich southern coastline Thursday, seizing an American and a Briton in the latest unrest to hit Africa’s leading crude producer, officials said.

The foreigners were seized shortly after midnight from a boat belonging to Petroleum Geo-Services, an oil field survey firm based in Oslo, Norway, that was working with oil giant Chevron Corp. to map the seabed for potential petroleum deposits.

The company said the rest of its crew aboard the ship were unharmed and that it was working to secure the release of the two hostages.

The company “is currently doing everything possible to solve this unfortunate situation,” it said in a statement.