In fact actress Ariah Agrawal who plays the lead character Anurag’s fiancé was involved in an unfortunate accident on the sets. Apparently, the actress was shooting for a scene in which she runs after Parth. She sees a photograph of Prerna, tears it, and throws it out of the window after burning it.

But somehow the burnt paper fell on the curtain and the whole mansion caught fire.
When everyone realized it, they all started running out of the building. Parth instantly saved Arian aka Mishka and the two ran out of the sets. The actress can't stop thanking God and her co-actor Parth Samthaan for his heroic deed.
Huge fire breaks out on the set of upcoming serial ‘Jhansi Ki Rani’
Speaking on the whole incident to a leading daily, Ariah said, "I never thought that the burnt piece of paper will catch fire like this. In the scene I am looking for Anurag who goes after Prerna and I reach his room to find a photograph of Prerna. I get very upset and burn her picture and throw it out of the window. But, unfortunately the curtain caught fire and in no time the Basu mansion was on fire."
On a related note, recently, the sets of the upcoming show Jhansi Ki Rani too caught fire and luckily there was no casualty.