The bus (Na 3 Kha 3307) had hit the truck (Na 4 Kha 3648) on Thursday evening.
District Police Office, Chitwan said bus help Umakar Prasad Bista, 35, and Roshan, whose surname is not known, from Sarlahi, are those dead.
Meanwhile, police have detained Min Kumar Newar, the driver, after his treatment.
Police said Mustak Ansari and another passenger were critically injured. All the injured are undergoing treatment at Chitwan Medical College, Bharatpur.
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