PARIS—At least seven people, including two children, have been killed in an explosion and subsequent fire that occurred in apartment buildings in southern France on Monday. Officials said a search is ongoing for at least two people who are missing. French Interior Minister Gérald Darmanin went to the site in the town of Saint-Laurent-de-la-Salanque and said about 30 people were wounded or suffered psychological trauma in the explosion that occurred around 2 a.m. Local radio France Bleu Roussillon reported that the explosion occurred on the ground floor of a two-story building, which was a grocery-sandwich bar. The fire then spread to neighboring buildings. Perpignan prosecutor Jean-David Cavaillé said it’s too early to know what caused the explosion but he mentioned the possibility that gas cylinders may have been present in the shop. An investigation is underway. Darmanin tweeted his “full support” for emergency services and said his thoughts were with …