From the Catholic News Agency:
Nearly two centuries ago, during a hot July night, one of the greatest churches in Rome was consumed by fire for over five hours. When the flames finally subsided, almost the entirety of the basilica had been destroyed.
Before the night of July 15, 1823, St. Paul Outside the Walls was the only papal basilica which could still boast its original 4th-century structure. The site of St. Paul’s tomb, it had been a major place of pilgrimage for centuries and was filled with valuable gothic and baroque artwork. The blaze, an accident, got started by a workman making repairs to gutters on the roof. Though Rome had a fire department, it took them two hours to arrive.