Officers on routine patrol in a police helicopter spotted the crop Tuesday under a canopy of trees about 3 miles from their hangar.
Police said Wednesday that the 1,000 or so plants had been days or weeks from being harvested. Once packaged, the crop could have been worth as much as $10 million.
Authorities say it will take a few days to remove all the plants.
Police typically try to intercept shipments of marijuana grown elsewhere. But they say they've never seen such a large illegal agricultural enterprise, largely because there isn't enough room in the city.