The arrests were made last night when they were trying to loot the bus. Of the four, Brijesh Mishra, Ravi Pratap Singh (both of Lakhimpur) and Sushil Khatri were involved in a number of crimes while Akhilesh Shukla is convicted with life imprisonment, they said.
Four pistols, ammunition and a car used by them were also recovered by the police.
Police is trying to elicit more information from them about their gang.