BAGRAM, Afghanistan -- U.S.-led forces intensified a sweep of southeastern Afghanistan for terror suspects Tuesday, capturing four suspected rebels and seizing a major weapons cache.

Hundreds of soldiers participated in Operation Valiant Strike, now in its fifth day, Lt. Col. Michael Shields said.

The cache, extracted from two walled compounds, included electronic detonators, timers, dozens of mortar and rocket-propelled grenade rounds and land mines. It was the fourth cache seized during the operation.

"We're looking at a potential facility where they were preparing ordnance perhaps to use against coalition forces or the government of Afghanistan," Shields, an operations officer, told The Associated Press. "This is a pretty significant find."

Four suspects were detained in connection with the cache, he said, but he declined to identify the groups they might be affiliated with.

Earlier Tuesday, Army spokesman Col. Roger King said another weapons cache found Monday included more than 170 rocket-propelled grenades and scores of land mines and mortar rounds.

About 600 U.S.-led soldiers are on the ground and hundreds more are providing support in the region as part of the offensive to hunt for suspected al-Qaida or Taliban fighters and their allies.

Eight people have been taken into U.S. custody since the operation began. There have been no clashes with rebel fighters and no soldiers have been injured, King said.

Regional Afghan official Gul Mohammed Khan said he understood that U.S. forces had moved to the Ataghar district from Maruf, where Taliban spiritual leader Mullah Mohammed Omar has tribal links. Ataghar is 95 miles east of the southern city of Kandahar.

Khan, district chief of Maruf, said the Americans had destroyed a large weapons cache Tuesday morning before leaving.

Just after midnight Monday, a patrol of U.S. forces from the Shkin base in the eastern Paktika province near the Pakistani border came under gunfire and grenade attack by as many as five militants, the Army officials said.

No soldiers were hurt, Shields said.

A Humvee was damaged after tumbling into a ditch to evade the fire, the officials said. A grenade landed underneath the vehicle, containing three soldiers, but did not detonate, Shields said.