Six Turkish members of a cargo ship’s crew have been kidnapped by pirates off the coast of Nigeria, a spokesman for the Nigerian navy said, Reuters informed. According to African officials cited by BBC, they are working with the Interpol and the country’s secret police to secure the crew’s release.

The vessel’s captain and the chief engineer were among those kidnapped, as the Nigerian navy confirmed; while the ship’s Turkish owners added that none of the crew were injured in the attack, but that they have no information on their whereabouts.

The ship, carrying chemicals, was believed to be travelling from Gabon to Ivory Coast, and was attacked by the pirates late at night as it was sailing close to the oil-rich Niger Delta.

In March, Nigeria and Equatorial Guinea agreed to establish combined patrols to bolster security in the Gulf of Guinea. The gulf is a significant source of oil, cocoa and metals for world markets, but pirates pose a threat to shipping companies.¬†They target oil tankers, usually seeking hostages for ransom and fuel to sell. Security analysts say the pirates have emerged from militant groups in Nigeria’s oil-producing Niger Delta, such as the Movement for the Emancipation of the Niger Delta.