The plantation is four times larger than the previous record discovery by authorities at a ranch in northern Chihuahua state in 1984.
The pot plants sheltered under black screen-cloth in a huge square on the floor of the Baja California desert, more than 150 miles south of Tijuana, across the border from San Diego.
The pot plants sheltered under black screen-cloth in a huge square on the floor of the Baja California desert, more than 150 miles south of Tijuana, across the border from San Diego.
Army Gen. Alfonso Duarte said the screening, which is often used by regular farmers to protect crops from too much sun or heat, made it difficult to detect from the air what was growing underneath.
It was only when soldiers on the ground reached the isolated area Tuesday that they found thousands of pot plants as high as 2.5 meters tall. The average height of the plants was about 1.5 meters. Duarte said they were not yet ready for harvest.
"We estimate that in this area, approximately 60 people were working. When they saw the military personnel, they fled," Duarte told reporters. A few were later reportedly detained at a nearby roadblock, but Duarte said no arrests were made at the scene.
He said traffickers could have harvested about 120 tons of marijuana from the plantation, worth about about $160 million.
Video of the plantation showed a sophisticated system of piped-in irrigation to support the plants, which Duarte said was fed by two wells. The plantation also included some wooden outbuildings, presumably for use by people caring for the plants.
Troops will destroy the fields by burning them, Duarte said.
The site is the near the coastal town of San Quintin. Journalists were en route there Thursday under army escort.
While it's unknown how much of Mexican drug cartels' income comes from marijuana, recent discoveries suggest it remains a large-scale trade.
