KABUL (AFP) - US and Afghan troops destroyed 2.5 tons of marijuana they found in an abandoned school in volatile southern Afghanistan, the US military said Sunday. The massive drugs stash was uncovered on Saturday during a joint US-Afghan operation against Taliban rebels in the Arghistan district of Kandahar province, spokesman US Colonel Greg Julian told AFP. "Afghan and coalition troops found and destroyed two-and-a-half tons of marijuana in a school in southern Afghanistan," Julian said. "The troops were on a foot patrol and they checked on this compound, the school and they found that stock of marijuana. They destroyed it the same day." Afghanistan produces more than 90 percent of the world's opium, most of which is turned into heroin and exported, and is also the world's second largest producer of hashish after Morocco, according to the United Nations. UN and Afghan officials say the drugs trade is supporting a Taliban-led insurgency, with rebels "taxing" farmers and also protecting trafficking routes and crops. In June, Afghan anti-narcotics police seized and destroyed 237 tons of hashish in Kandahar province " said to be worth about 400 million dollars " in what was believed to be the biggest haul of its kind in the world. Afghan and international troops dismantled an illegal drugs-making facility in the province last month, destroying another 40 tons of hashish.