The explosion triggered a fire which was doused after three hours of efforts, police said.
The armoury was completely destroyed, said deputy inspector general of police D K Arya.
He said the explosion was of such a high intensity that even a tree outside got uprooted.
A few seized two-wheelers were gutted in the fire.
According to initial probe, the container of seized country liquor, which primarily contains spirit, might have exploded in the hot weather.