At least 30 people were injured when the bus they were travelling in collided head-on with a truck near the Hayatnagar bridge in the district's Alapur area, police said on Saturday.
The Uttar Pradesh State Road Transport Corporation bus was on its way to Delhi from the Hardoi depot.
The accident occurred around 2 am, Superintendent of Police (City) Amit Kishor Srivastava said.
There were 50 passengers on the bus. The front portions of both vehicles were severely damaged under the impact of the collision, he added.
Srivastava said 30 passengers were injured. Of them, 20 suffered serious injuries and have been hospitalised.