By Ben Marcus, Julia Jones and Tiffany Ap CNN

PARIS (CNN) - An explosion and subsequent fire ravaged a bar in northern France early Saturday, leaving 13 people dead and several others injured, authorities said.

Initial reports indicate the explosion in Rouen, Normandy, was accidental, according to the Rouen Police Department.

Following the incident, a major street was blocked and a security perimeter set up around Le Cuba Libre Bar, a witness said. Fire trucks and several police vehicles swarmed around the bar on Avenue Jacques Cartier.

Local media reported the bar was hosting a birthday party at the time, and the victims were between the ages of 18 and 25.

French President François Hollande conveyed his condolences in a tweet. "I express my solidarity and compassion to the victims' families."

France has been on high alert following several fatal terror attacks. About two weeks ago, two jihadist attackers killed a priest in Rouen.

During Bastille Day celebrations on July 14, a man who pledged allegiance to ISIS drove a large truck through crowds gathered to watch fireworks in Nice, killing at least 85 people.

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