PARIS -- Paris police say a letter bomb exploded at the French office of the International Monetary Fund, lightly injuring one person.

A police official said no other damage was been reported in the incident in western Paris on Thursday. It is unclear who sent the letter. Police experts are at the scene, said the official, who was not authorized to be publicly named.

A police official said the IMF had received threatening telephone calls recently, but it wasn’t yet clear whether there was any connection to the letter bomb.

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The IMF office in France did not immediately respond to calls.

France remains in a state of emergency after a string of deadly Islamic extremist attacks over the past two years.