A plane has crashed into a supermarket car park in Portugal. The aircraft - which was carrying four people - is said to have exploded in mid-air. It came down on a truck unloading in the Lidl Supermarket in Tires near the coastal town of Cascais 20 miles west of Lisbon, killing the driver. The spot where the plane crashed is just 150 metres from a local school. All four people on board the plane that exploded in mid-air before crashing to the ground are confirmed dead. It is understood three other people on the ground when the plane crashed have suffered minor injuries. "Everything indicates that an explosion occurred in the air", a Civil Protection source told Correio de Manha. The newspaper reports the plane belonged to a Swiss company that makes orthopaedic prostheses and was headed to Marseilles. At least one house in the area of the crash is reported to be on fire. Portuguese president Marcelo Rebelo de Sousa has arrived at the scene. A round 80 firefighters are at the scene along with other emergency workers. The Swiss-registered plane, a Piper PA-31TR Cheyenne II, is said to have left Geneva three days ago before making a stop in the southern French port city of Marseille and continuing on to Tires. Filipa Ribeiro, daughter of the owner of a pizzeria that is just 200 metres from the scene of the accident, told Correio de Manha she heard "a big bang" at around midday. "A customer of ours saw the plane crash," she added. The pilot was initially described as French although subsequent reports pointed to all four victims being Swiss. The alert was sounded at five minutes past midday. Several vehicles are also understood to have caught fire. Video footage taken by onlookers showed huge plumes of black smoke rising into the air from the scene of the crash. A witness told Portuguese TV the owner of a house which caught fire in the tragedy was able to run out of her property with her baby in her arms. Another lady, known only as Alexandra, who was inside the Lidl supermarket, said: "Everything started shaking like an earthquake and people began to scream and run in all directions." The plane, believed to be registered in Switzerland, had just taken off from an aerodrome in Tires. The victims are being reported locally as the pilot and three passengers. A Twitter user who claims to have seen the crash said:"I saw the plane going down!! I think it fell more or less on top of the Lidl. "I don't think I've ever felt like this." Another added: "The plane fell near my house, smells like intense burning." According to Lusa, the official source of the Office of Prevention and Investigation of Accidents, the aircraft took off from Tires aerodrome and about two thousand metres after takeoff.