The incident took place in Farookh Nagar locality in Sahibabad.
Police said the explosion took place in the car in which fire crackers were kept to be taken to a wedding.
Car owner Mohammad Rizwan — who has a business of manufacturing fire crackers — had allowed five children from his family and neighbours to listen to music in the car.
When one of the children switched on the music system, a blast took place in which four children died on the spot and another sustained critical burn injuries.
The deceased children were identified as Akshha (6) and Farhan (8), daughter and son of Rizwan; Sarika (3), daughter of Furkan; and Farhan (8), son of Mohammad Sajid.
The other child, Krishh (7), son of Praveen, was rushed to a hospital where doctors said his condition was critical.
R.K. Bhardwaj, a doctor attending to the injured child, said his condition was critical, “but we are trying hard to save his life”.
Police said that prima facie it appears that the explosion occurred due to an electrical short circuit in the music system.
A criminal case against Rizwan has been registered at Sahibabad police station and he has been asked to present all necessary documents related to the manufacture of fire crackers, said Ghaziaabad Superintendent of Police Ajay Pal.
The bodies of the children have been sent for autopsy.
Police said a thorough screening has been ordered in the entire Farookh Nagar area, where fire crackers are being manufactured as a cottage industry.