Five persons, including a police constable, were killed on the spot when the vehicle in which they were travelling crashed against a tree.
The accident took place late on Sunday night on the Pratapgarh-Patti road under Kandhari police circle.
Additional Superintendent of Police (East) Surendra Dwivedi said on Monday that the driver lost control over the vehicle leading to the accident.
The victims have been identified as constable Sandeep Kumar Yadav, 29, Sandip Yadav, 26, Akhilesh Yadav,35, Rahul Yadav, 28, and the driver of the ill-fated vehicle Pappu Yadav.
The accident happened when they were returning from a wedding ceremony near the Dewan Mau village.
All the bodies have been sent for post-mortem.