An explosion and subsequent fire ravaged a bar in northern France early Saturday, leaving 13 people dead and several others wounded, authorities said.

Initial reports indicate the explosion in Rouen, Normandy, was accidental, according to the Rouen Police Department. The fire is thought to have been caused by the candles on a birthday cake. Reports said the fire broke out in the basement of the Cuba Libre where the private party was being held on Friday night. At least six people were rescued and received treatment for injuries. The victims were described as being aged between 18 and 25.

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

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