The five people consumed sattu at a road-side shop and soon started vomiting, the sources said.
While a man, identified as Pappu, died on way to being taken to the Sadar hospital, two others -- Sansad Das and Krishna Kumar -- succumbed to illness during treatment in the same hospital, the sources said.
Two others, Tribhubhavan Das and Umesh Sharma, were admitted in the Sadar hospital where the attending doctors referred Das to the PMCH at Patna, they said.
A Sadar hospital doctor K K Rai said it was a case of food poisoning due to consumption of contaminated sattu.
All the victims were daily wage labourers, the sources said, adding an investigation was going on in the matter.