At least seven people, including two children, have died after an explosion sent fire raging through a building in southern France. One of the victims of the blaze that started in a three-story building in the coastal town of Saint-Laurent-de-la-Salanque, north-east of Perpignan, was reported to be a baby. The French interior minister, Gérald Darmanin, who was on an official visit to police in Montpellier, 96 miles (155km) from the tragedy, was expected at the scene on Monday afternoon. He confirmed the provisional death toll of seven people including two children but added: “Unfortunately, the work of the firefighters and other services is not finished so this may not be definite.” The French prime minister, Jean Castex, sent his condolences to the victims’ families and friends and praised the work of the emergency services who he said were working “in difficult circumstances”. The explosion happened around 1.30am local time and was believed to have occurred on the ground floor, which housed a grocery store and a fast-food take-away. Flames quickly engulfed the building and two neighbouring properties. Firefighters have searched two of the buildings but said the third remained too dangerous to enter. Jean-David Cavaillé, the Perpignan public prosecutor, said the emergency services were still searching for a family thought to be in the building but who may have been absent. The search was being hampered because temperatures in the buildings remained high and several floors had collapsed, he said, adding that the death toll may rise further. Cavaillé said an investigation into the cause of the explosion had been opened but it was too early to establish whether it was accidental or criminal. One man who jumped from the second floor to escape the flames was said to be in a critical condition in hospital. Three other people were also injured. Just under 100 firefighters were called to the scene in the early hours of Monday. A resident of a neighbouring building who was woken by the explosion said it was “a horror scene … it was extraordinarily violent”.