KARACHI: Initially reported as an act of terror, the attack on a private school in North Nazimabad area of the metropolis turned out to be a firecracker explosion by high-school students, with the police arresting five students on Monday over their alleged involvement in the incident.

According to DIG West Feroz Shah, five students of Educators campus-I in North Nazimabad were taken into custody after the investigation into the reported grenade attack revealed that the students brought firecrackers in a bid to play a prank, following the school administration's refusal to let them appear for upcoming examinations over non-payment of school fees.

"The police took one injured student into custody for investigation, since he was the only one injured in the incident and the student confessed that he and other students had bought firecrackers which exploded accidentally," said the DIG.

The incident was reported on Friday along with two other minor blasts, one at police station in Gulshan-i-Iqbal, and the other at girls’ college in Karimabad.

Related: Cracker blasts at police station, school, college sow fear

Feroz Shah said police is mulling legal options as all the five suspects are under-age and cannot be tried for terrorism, especially after the revelation.

A bomb disposal squad official who reached the site of blast on Friday had said that the 'explosive device' appeared so small that he would liken it to a firecracker.

Speaking to Dawn, Counter-Terrorism Department officer Raja Umer Khattab, who had examined all three sites also expressed ‘scepticism’ about the explosion at the school, which is situated two-and-a half kilometres from the Apwa college.

He quoted witnesses as telling police investigators that they did not see anyone throwing a cracker or any other explosive device into the school and that they just heard the blast. It appeared to be a ‘firecracker’ that injured the student, he had asserted.