The weapons cache was discovered about 2.5 miles south of four caves in Paktia province that were jam-packed with tens of thousands of rockets and other ordnance, and which British military engineers obliterated Friday in what they described as one of their largest controlled explosions since World War II.
Lt. Col. Ben Curry, of the British military, said the new find contained about 60 107mm rockets, 100 82mm mortar rounds and 12 boxes of 12.7mm heavy machine gun ammunition.
"This cache was destroyed this morning by the bomb disposal team," he told reporters at Bagram, the main base for the U.S.-led coalition.
A few rocket-propelled grenades and some small-arms ammunition found in a culvert under the main road linking two cities in the province, Khost and Gardez, were also destroyed in a controlled blast, he said.
The three-week-old British-led mission, known as Operation Snipe, is part of Operation Mountain Lion, the U.S.-led search for Taliban and al Qaeda holdouts in eastern Afghanistan. The mission is backed by Afghan forces, U.S. special operations troops and U.S. air support.
British Royal Marines scouring mountains in eastern Afghanistan for vanished Islamic militants have covered 80 to 85 percent of the ground they were told to sweep, a spokesman said on Sunday.
Marine Lieutenant Colonel Ben Curry said the commander of 45 Commando leading the 1,000-strong manhunt and intelligence gathering mission estimated he had walked 125 miles since Operation Snipe began 15 days ago.
But in a country where the mountains and hillsides are honeycombed with caves that have been used for decades to hide arms for warlords, Islamic rebels, the Taliban and al Qaeda, few coalition commanders have any illusions about searching through them all.
"We'd have to be here for a hundred years," said British Lt. Col. Tim Chicken said, looking out over an expanse of desolate hills covered with desert shrubs in southeastern Afghanistan.
The search for arms caches is a daunting task in a country where every hill and mountain seems filled with tunnels, caves and underground bunkers. Rivers said searching them all is out of the question.
"It's not conceivable to search an area the size of Texas overnight. It's literally filled with caves. It's definitely a long-term process," he said.