At least 18 people were injured when a bonfire exploded at a carnival held in northern France. The blast occurred at the end of the Yellow Carnaval in Villepinte, north-east of Paris, yesterday. <br/><br/>A mother and her child are among those seriously injured and the town's mayor was also hurt. An initial investigation has been started but the cause of the explosion is not yet known.<br/><br/>A police source said that the explosion may have been caused by the petrol used to help start the fire.<br/>