The most probable tradition is that Porsena, knowing the City to be without food owing to the long investment, made the Romans a present of his richly-stored camp, in which provisions had been collected from the neighbouring fertile fields of Etruria. Then, to prevent the people seizing them indiscriminately as spoils of war, they were regularly sold, under the description of "the goods of Porsena," a description indicating rather the gratitude of the people than an auction of the king's personal property, which had never been at the disposal of the Romans.
Hor Book II Chapter 14: Final Attempt to restore the Tarquins.