After Kaliya went away, the inhabitants of Vraja and the cows spent that night near the banks of the Kalindi (Yamuna). In the course of that night a wildfire broke out in the forest, dried with summer heat. The Vrajavasis, scorched by the fire, were bewildered. They seek Krishna's help, believing that he was their only refuge. "Protect us, O Krishna and mighty Rama -- this most terrible fire is consuming us."
Krishna swallows the fierce conflagration, as a mere sport.
This fire was meant to clean up the whole environment which was polluted with Kaliya's poison.