CHICAGO — In Chicago, a bustling urban metropolis where skyscrapers are as likely to sprout up as anything a farmer might plant, someone decided there was just enough room to grow something a little more organic: Marijuana.

The plants grew even taller than the tallest Chicago Bulls. However, just days before the crop on a chunk of land the size of two football fields would have been ready to harvest, a police officer and county sheriff's deputy in a helicopter spotted it as they headed back to their hangar about three miles away.

On Wednesday, a day after the discovery of the largest marijuana farm anyone at the police department can remember, officers became farmers for a day as they began to chop down about 1,500 marijuana plants that police said could have earned the growers as much as $10 million.