SB 9.8.11

sva-śarīrāgninā tāvan
 mahendra-hṛta-cetasaḥ
mahad-vyatikrama-hatā
 bhasmasād abhavan kṣaṇāt
Synonyms: 
sva-śarīra-agninā — by the fire emanating from their own bodies; tāvat — immediately; mahendra — by the tricks of Indra, the King of heaven; hṛta-cetasaḥ — their consciousness having been taken away; mahat — a great personality; vyatikrama-hatāḥ — defeated by the fault of insulting; bhasmasāt — turned to ashes; abhavan — became; kṣaṇāt — immediately.
Translation: 
By the influence of Indra, the King of heaven, the sons of Sagara had lost their intelligence and disrespected a great personality. Consequently, fire emanated from their own bodies, and they were immediately burned to ashes.
Purport: 

The material body is a combination of earth, water, fire, air and ether. There is already fire within the body, and our practical experience is that the heat of this fire sometimes increases and sometimes decreases. The fire within the bodies of the sons of Sagara Mahārāja became so much hotter that all of them burned to ashes. The fire’s increased heat was due to their misbehavior toward a great personality. Such misbehavior is called mahad-vyatikrama. They were killed by the fire of their own bodies because of insulting a great personality.