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The gunfire was reported in a suburb of Marseille in southern France

Castellane is known for its drug-related activity

CNN  — 

Gunmen fired on police in a suburb of the southern French city of Marseille on Monday, the prosecutor’s office said.

Shots were directed at a police car, and police returned fire, according to prosecutors. There were no immediate reports of casualties.

A SWAT team was sent to the scene.

The gunfire erupted in Castellane, a suburb in northern Marseille that’s known for its drug-related activity.

France has been under a heightened state of alert since last month’s terror attacks in Paris that killed 17 people.

French Prime Minister Manuel Valls is scheduled to be in Marseille later Monday.