Seven students were injured as an explosion took place at the chemistry lab of Naogaon Polytechnic Institute on Sunday.

The injured are identified as Atikur Rahman, Rakibul Islam, Rafi Akhter, Shafiqul Islam Shafi, Niyamul Islam, Touhid Shahriar and Sadiqul Islam Shafi. They all are third year students of Computer Technology department at the institute.

Fazlur Rahman, principal of the institute, said the explosion took place around 5:30pm when the students were attending a practical examination at the lab.

Other teachers and students rescued the victims and took them to Sadar Hospital immediately, he said.

Dr Saiful Islam, a surgery specialist at the hospital, said three of the injured are in critical condition and they sent to Rajshahi Medical College Hospital for better treatment.