ROME: The death toll from an explosion at a fireworks factory in southern Italy has risen to nine after one of those hurt succumbed to his injuries Sunday, a hospital source said.

Seven people were killed on the spot and several others were injured on Friday in the explosion in the southern port city of Bari, local media reported citing the emergency services.

Another person who was seriously injured in the blast died on Saturday.

La Repubblica newspaper reported that a van exploded first, triggering a series of blasts within the factory that lasted around an hour.

The Bari prosecutor's office has opened an involuntary homicide enquiry into the explosion.

Italian President Sergio Mattarella said everything would be done to ensure that the cause of the tragedy would be discovered "as soon as possible".

Two Canadair water-bomber planes were deployed to prevent the fire triggered by the blasts from reaching a nearby forest.

One of the injured sustained burns on 90 percent of the body, La Repubblica said.

The factory was totally destroyed.

Such explosions are a relatively regular occurrence in Italy, costing several lives each year.

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