Pirates have hijacked an oil supply ship working with Chevron Corp. off Nigeria and took three people hostage, the company said Friday. A group of eight armed pirates boarded the vessel on Thursday night, attacking the crew and taking three people hostage, the company said in a statement. The vessel, the MV C-Endeavour, belongs to U.S. firm Chouest. The attack was the second by gunmen on Chevron-contracted vessels off the coast of the Nigerian coast in a month. The frequent attacks on ships by pirates in the Gulf of Guinea pose increasing threat to security in the region as a trade hub.