The incident took place near Malvika Steel factory when the nine persons were on their way to Kanpur from Jaunpur this morning, they said.
Rehana Khatoon (40), Alfia (8) and Fakre Alam (25) died on the spot, police said.
Of the six seriously injured persons, one succumbed while being rushed to Lucknow Trauma Center, police said, adding his identity was not immediately known.
Hunt has been launched for the truck which sped away after the accident, police added.
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