"The incident occurred at around 9.30 am when the three children were cooking tomato curry in their kitchen just for fun when their parents were away," Jubilee Hills Police Station Inspector S Venkat Reddy said.
As they placed firewood, one of the girls poured spirit (inflammable liquid) on it. Thereafter when they ignited the firewood, there was a sudden explosion and the children were trapped in the fire, Reddy said.
The injured boy Yogi, who is in a critical state, is currently undergoing treatment at a hospital, the police officer said.
"Narasamma's mother, who had brought the spirit, used to put some drops of the liquid on the firewood before cooking to flare up the flames. It seems the girl today poured the entire tin on the firewood resulting in the mishap," Reddy explained.
A case was registered and probe is underway, police added.