The district hospital has officially confirmed the death of 13 passengers in the accident.

However, officials said that given the fragmented condition of the remains, the actual number of victims could increase once they receive the DNA test reports.

"Only after DNA testing of all the remains will it be possible to ascertain how many individuals they belong to. Identification will be confirmed after matching with the samples provided by family members," Dr Garg said.

Assistant Regional Transport Officer Madan Sharma said Sunil Kumar (45), who was driving the Azamgarh-bound bus involved in the crash, was missing.

The second driver and the conductor were admitted to the hospital with injuries, but they have no recollection of the incident.

"They told us they fainted immediately after the collision and regained consciousness only after being hospitalised. They are unable to say what happened to Sunil Kumar, whether he was injured or died in the crash. His fate may become clear after examination of the burnt remains," Sharma said.

A passenger, Parvati (42) from Rath tehsil in Hamirpur district, also remained untraceable.

Her brother-in-law Gulzari Lal searched for her till late on Wednesday evening across hospitals and mortuaries, but no information could be found, officials said.

In another case, Kanpur resident Pooja has lost her brother-in-law Anuj Srivastava, who was travelling with her on the bus.

With several passengers still unaccounted for and identification of remains pending, officials said the possibility of an increase in the death toll cannot be ruled out.