Giving benefit of doubt to the accused, Additional Sessions Judge H S Grewal said that the evidence produced by the prosecution on record was not sufficient to convict them.
Those acquitted were Gurpreet Singh, Harvinder Singh Khalsa and Ramminder Singh Rinku.
The fourth accused, Sandeep Singh Herry, had died in Nabha jail during trial.
In the blast on October 14, 2007, six persons had lost their lives and 42 others had sustained serious injuries.
FIR was registered on that day on the complaint of cinema manager Gopal Krishan.
