Duryodhana’s plan was to burn the palace in flames and kill the five Pandavas along with their mother in Varanavata.
Vidura had secretly constructed a tunnel with the help of a few trusted workers underneath the palace in order to help the Pandavas, and had warned the Pandavas, who were cautious of their surroundings.
A Nishadha woman and her five sons had resided with the Pandavas in the Lakshagriha Palace.
Purochana was assigned the job to burn the palace in flames, but Bhima had set it on fire before he could.
The Pandavas, along with their mother Kunti, who was carried by Bhima, escaped through the tunnel, while Purochana died being caught in the fire.
But the Nishadha woman and her sons were caught in the fire, and their death was totally unintended.
The residents of Varanavata assumed the bodies of the Nishadha woman and her five sons to be those of the five Pandavas and Kunti.
This assumption helped the Pandavas and Kunti to live incognito as wanderers.