The government also said the involvement of criminal elements connected with naxal organisation People's Liberation Front of India (PLFI), which is active in neighbouring Jharkhand, has come to light and efforts are on to nab all the people involved in the incident.
"The investigations till now indicate that main accused of the incident, Kundan Kumar and a few other criminal elements wanted to use the IEDs in the state capital to create an atmosphere of terror and extort money from the people. The IEDs were brought from Jharkhand," Water Resources Minister Vijay Kumar Chaudhary said.
An FIR in the case was registered at Agamkuan police station in the city under various sections of Indian Penal Code, Explosive Materials Act and Unlawful Activities Prevention Act (UAPA).
Nobody was killed or injured in the incident.
Opposition BJP had demanded government's version on the blast on April 1.
Meanwhile, Bihar Police achieved a breakthrough in the case when they arrested main accused Kundan from Ekangarsarai area in Nalanda district on April 3. Subsequently, his four associates were also nabbed and sent to judicial custody.