Nawada Superintendent of Police Parvez Akhtar said the incident happened at St Joseph Inter School when the flag hoisting ceremony was on. Among the injured girls one is a student of class eight, while another is of class two.
"Anti-social elements attacked the ceremony and lobbed two bombs at students and teachers assembled in the school premises. The two girls sustained injuries in it. There was a melee after the bomb attack," Akhtar said.
The officials are also investigating about reasons and motives behind the incident, he said.
Meanwhile, the two injured girls have been admitted to a private clinic for treatment and their condition was stated by doctors to be out of danger.