ROME — A blaze on Friday at a small laboratory in central Italy that treats marijuana so it can be used medically left a man dead, three injured survivors and a woman missing, Italian firefighters said.

Flames raged through a small building in the countryside outside Gubbio, a town in the Umbria region.

Firefighters were searching into the night for a woman who was reported missing, said state firefighters spokesperson Luca Cari. Much of the fire had been extinguished, he said.

RAI state TV said the fire apparently was caused by a gas explosion.

Cari said it wasn’t immediately known what touched off the blast.

RAI state TV said that the most severely injured survivor was flown by helicopter to a hospital with a specialized burns center.