The investigation into an explosion in the washroom of a school in Chhattisgarh revealed that five students, including three girls, orchestrated the blast by planting sodium metal to target a female teacher they are upset with, police said on Tuesday.

A class IV girl student was injured in the explosion which occurred in the washroom of a private school in Mangla area of Bilaspur city on February 21.

Following a thorough investigation and examination of CCTV footage, the police detained four of the five involved students on February 23. A fifth student, who had gone to visit relatives, is yet to be detained.

The four detained children, all class 8 students, were produced in a juvenile court which sent them to the juvenile home, a police officer said.

"The involvement of five students, including three girls, surfaced during investigation and examination of CCTV camera footage following which four of them were detained on Sunday (February 23)," said Bilaspur Superintendent of Police Rajnesh Singh.

He said the five students had allegedly planned the blast to target a female teacher of the school with whom they were upset for some reason.

They watched an online video about how sodium metal could trigger an explosion when in contact with water, he said.

One of the students purchased sodium metal through an online shopping platform using her relative's ID. They placed the sodium metal at the outlet of the cistern in the washroom, the police officer said.

"A class IV student, who was not the intended victim, used the flush, inadvertently triggering the blast that left her injured," he said.

The school’s teachers, who were busy overseeing final exams, rushed to the washroom after hearing the explosion and found the injured girl lying on the floor.

Further investigation into the matter is underway, he added.

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