An American worker kidnapped in Nigeria's oil rich southern Delta region has been released after being held a week.

The U.S. embassy said Friday the 50-year-old man is in a safe location. The circumstances surrounding his release have not been announced.

During the kidnapping in Nigeria's Warri State, the man's driver was shot and killed. The suspects then contacted the man's employer demanding more than $300,000. There has been no word if a ransom was paid.

Earlier this month, the U.S. State Department issued a warning to citizens to avoid travel to the Delta region of Nigeria because of the risk of kidnappings, robberies and personal attacks. The State Department announced in its most recent warning that five U.S. citizens were kidnapped in Nigeria last year.