Officers discovered the cannabis this morning, Wednesday, after having been called to the site of what was previously The Fairway pub, on Warmsworth Road, Balby to deal with an unconnected matter.
They were initially called to deal with a group of people throwing stones in the area.
But the building, which is no longer open as a pub, was found to contain around 2,000 cannabis plants. Police said they were being cultivated inside the building, which is no longer used as a pub.
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Doncaster central neighbourhood Insp Lynne Lancaster said the drugs had been seized and would be destroyed.