From BBC News:
The men, seized from the offices of China’s National Petroleum Company, were freed after “complex efforts”, China’s foreign ministry said. All nine were safe and well and were handed back to their company in Bayelsa state, a ministry statement said.About 100 foreign hostages, mostly oil workers, have recently been kidnapped in the oil-producing Niger Delta.
Many Niger Delta residents live in poverty, and taking hostages for ransom has become increasingly common. [Full Text]