Pirates are the main threat to oil company workers located off the coast of Nigeria, but they are unfortunately not the only danger. Chevron has just announced that 12 crew are missing after a tug boat under contract to the San Ramon-based oil major capsized on Sunday morning.

According to Reuters, the Jascon-4 tug, owned by West African Ventures, was “performing towing operations” around 30 kilometres off the coast of the Niger Delta when it capsized and sank in the “heavy ocean swells.”

As spokeswoman for West African Ventures stated that, “unfortunately all twelve crew members are still missing.

Rescue operations involving sea divers are still on-going and a full investigation into the incident is taking place.”

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Reuters tried to question Chevron Nigeria about the incident, but they were unwilling to give any update.

Nigeria is the largest oil producing country in Africa and oil revenues have helped to develop its economy and infrastructure.

Chevron, in various joint ventures with the Nigerian National Petroleum Corp, spends about $3 billion each year on its on and offshore operations; which in 2012 produced a total of 238,000 barrels of crude oil, 165 million cubic feet of natural gas and 4,000 barrels of liquefied petroleum gas.

By. Charles Kennedy of Oilprice.com