It is uncertain who or what actually caused the fire — whether accident or arson . Suetonius and Cassius Dio favor Nero as the arsonist , so he could build a palatial complex . Tacitus mentions that Christians confessed to the crime , but it is not known whether these confessions were induced by torture . However , accidental fires were common in ancient Rome . In fact , Rome suffered other large fires in 69 and in 80 .