Apparently for a shoot sequence, some diyas were to be used in the backdrop. 

Sanjay Leela Bhansal

When Bhansali realised that oil was being used in the diyas, he threw a fit.

According to him, only ghee needs to be used for lighting diyas! Unit hands then emptied the oil from the diyas and poured pure ghee into it. It was only then that the taskmaster Bhansali kept cool!