Soldiers discovered 23 marijuana fields and seized 40 tons of harvested pot in the northern state of Durango, Mexico's National Defense Secretariat, or Sedena, said.

The fields, covering a total of 60 hectares (148 acres), were found Saturday in the municipality of Santa Maria del Oro, Sedena said in a statement.

Along with the 40 tons of pot, troops confiscated two rifles, ammunition, 26 military-style uniforms, five vehicles and a laboratory.

Sedena did not mention any arrests in connection with the operation.

Earlier this month, troops in the northwestern state of Baja California discovered the biggest marijuana plantation in Mexico's history.

The 120-hectare (296-acre) spread had the potential to yield 120 million tons of marijuana worth roughly $158 million, the commander of Mexico's 2nd Military Region, Gen. Alfonso Duarte Mujica, told the press.

The plantation was found on the south side of Ensenada, near the U.S. border, just 2 kilometers (1.6 miles) from the main north-south highway in Baja California, the general said.

Mexico, the main conduit for illegal drugs entering the United States, produced roughly 19,000 tons of marijuana in 2009, according to official estimates.

Besides domestically produced marijuana, heroin and crystal meth, Mexican drug cartels traffic in cocaine and heroin from South America.

More than 40,000 people have died in Mexico since December 2006 in a conflict pitting rival drug cartels against each other and the security forces.