Updated

Private security sources tell The Associated Press that pirates have seized an oil tanker off the coast of Nigeria's oil-rich southern delta and kidnapped the foreign crew.

The sources, who spoke on condition of anonymity because they were not authorized to discuss the seizure with journalists, said the attack happened off the coast of Port Harcourt.

An unknown number of foreign crew members remained held Thursday as the pirates offloaded the tanker's oil cargo. The tanker was identified as the MT Halifax, a ship flagged out of Malta. The Associated Press could not immediately reach the ship's owner Thursday.

Analysts say the area has seen a growing trend of oil tanker hijackings as pirates target legal and illegal oil shipments moving out of Nigeria.

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