Police said the bomb, similar to the one recovered recently near the residence of Minister of state in PMO V Narayanaswamy in Puducherry, was a "powerful one".
It had 3.5 kgs of explosive gel and 14 detonators.
It was suspected that the planting of the bomb could be the handiwork of Naxalites or some traders, who did not want the supermarket to function as it affected the small traders, police said.