Philo says that the smoke of Sodom and Gomorrah was still rising in the first century:
And a most evident proof of this is to be found in what is seen to this day: for the smoke which is still emitted, and the sulphur which men dig up there, are a proof of the calamity which befell that country; while a most conspicuous proof of the ancient fertility of the land is left in one city, and in the land around it.
Therefore on this occasion, as the holy scriptures tell us, thunderbolts fell from heaven, and burnt up those wicked men and their cities; and even to this day there are seen in Syria monuments of the unprecedented destruction that fell upon them, in the ruins, and ashes, and sulphur, and smoke, and dusky flame which still is sent up from the ground as of a fire smouldering beneath;
Wisdom of Solomon 10.7 says the same thing:
Evidence of their wickedness still remains:
a continually smoking waste-land,
plants bearing fruit that does not ripen,
and a pillar of salt standing as a monument to an unbelieving soul.