Finally the lead comes through. The last body had traces of 'substance-x' which is used in making 'product-y'. And yes, there just happens to be an abandoned 'product-y' factory on the outskirts of town - it is always on the outskirts of town.
Here is a hint, check all the abandoned factories on the outskirts of town from the get-go; you can save yourselves a lot of hassle!