The Mexican army says it has discovered a huge field with mature marijuana in the northern state of Baja California.
Soldiers were patrolling the area, some 300km (190 miles) south of the US border, when they found the plantation.
The field near the town of San Quintin, measuring 1.2sq km (300 acres), was surrounded by a hedge of cacti. It is the largest marijuana plantation ever found in Mexico, officials say.
They say it would have yielded a harvest worth about $160m (£99m).
A Mexican army spokesman told the BBC it was unclear who owned the territory.
An estimated 60 people were working on the plantation, said the local army commander, Gen Alfonso Duarte.
"When they saw the military personnel, they fled," he told reporters.
The Mexican army has led the war on drug gangs launched by President Felipe Calderon in December 2006.