KABUL, Afghanistan — NATO-led troops and Afghan police seized over nine tons of marijuana from a truck in southern Afghanistan, the alliance said Wednesday.

Four people in the truck were detained, NATO said. No date was given for the seizure in Zabul province, on a road between the southern city of Kandahar and Kabul.

In the country's west, U.S. and Afghan troops recovered over 120 pounds of opium from a car in Farah province, another NATO statement said Tuesday.

The U.S. soldiers were supporting an Afghan army checkpoint when a car failed to stop, the statement said. An Afghan soldier noticed a suspicious bag where the spare tire was supposed to be and alerted the next checkpoint, where the car was searched and the driver and passenger detained.

Afghanistan grew 59 percent more opium this year, yielding a record crop of 6,100 tons, according to the U.N. Office on Drugs and Crimes.

The agency said that is enough to make 610 tons of heroin, outstripping world demand by a third.

Some 2.9 million Afghans, or 12.6 percent of the population, are involved in opium cultivation. The U.N. predicted revenue from this year's harvest would top $3 billion.

Opium cultivation has surged since the Taliban was ousted in late 2001. The former regime had virtually eradicated the crop with a ban it enforced by jailing farmers.

But Taliban-led militants are now implicated in the drug trade, encouraging poppy cultivation and using the proceeds to help fund their insurgency, Afghan and Western counter-narcotics officials say.