Update : The video turned out to be fake, full story here. A Redmi Note 4 exploded, caught fire and the whole incident was captured on camera. There are several videos about the same on YouTube. This happened in Bangalore at a local mobile store on 17th July.
The video was captured via the store CCTV camera. In the video you can clearly see the owner handing over the handset to the store person and when the store person tries to eject the SIM the handset explodes and catches fire.
Thankfully no one was injured in the blast, the phone that fell down was still on fire. Xiaomi is investigating the incident, the authenticity of the video could not be verified. This is a strange incident cause usually the handset blast happens when the handset is being charged. But this seems the first time when the handset exploded when eject the SIM.
This definitely is a battery problem on the Redmi Note 4 cause that is the only thing capable of exploding, may be the battery structure got compromised and gases started building up inside, the SIM ejection probably acted like a detonator.
Whatever may be the reason Xiaomi will be investigating this issue and will respond later on.
This is a isolated incident, and this has happened with many top end brand, few such incidents hardly make a difference, unless it is happening on a larger scale.
According to techcase the smartphone owner confirmed the incident.
Source : Youtube