Chief Public Relations Officer, East Central Zone, Rajesh Kumar, said the accident took place at Sahadai Buzurg, close to Mahanar Road in the Sonepur division.
One general coach, one AC coach B3, three sleeper coaches - S8, S9, S10 and six more coaches have derailed, he said.
Commissioner Railway Safety (Eastern Zone), Latif Khan, will conduct an inquiry into the accident, Kumar said.
Principal Secretary, Disaster Management Department, Pratyay Amrit said seven people have died in the accident.
"The identity of the deceased was yet to be confirmed. Rescue operations are in full swing and an accident relief train has been sent to the site of the mishap. A team of the NDRF has also reached the spot," Kumar said.
Adequate number of doctors are available at the site. Ambulances have been pressed into service, he said.
Twenty-four people have been injured in the accident, Superintendent of Police Manavjit Singh Dhillon said.
The injured were rushed to a hospital here, where the doctors referred the seriously wounded to Muzaffarpur and Patna.
Teams of doctors have also rushed from Sonepur and Barauni to the accident site, Kumar said.
The office of Railway Minister Piyush Goyal has announced Rs 5 lakh ex gratia each to kin of those killed, Rs 1 lakh each to the grievously injured people and Rs 50,000 each to those who received simple injuries.
Local residents were aiding rescue teams in carrying out operations.
Bihar Chief Minister Nitish Kumar, who expressed deep condolences over the deaths, said, "The district magistrate and the superintendent of police have rushed to the spot and are overseeing the relief work in coordination with the Railways."
The 12 unaffected bogies are being moved to Hajipur where more coaches will be attached to the train and thereafter, it will leave for the onward journey, the officials said.
The Railways have issued helpline numbers - Sonpur 06158221645, Hajipur 06224272230 and Barauni 06279232222.
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