U.S. forces acted on a tip about an Iraqi weapons supply Thursday and ended up discovering a much larger find — a hidden cache of buried surface-to-air missiles and mines.

Military officials are still tallying the cache but have retrieved at least 317 4-foot rockets and 220 anti-tank mines. Fox News had exclusive access to the military during the operation about 45 miles south of Baghdad.

Earlier Thursday, one U.S. soldier was killed and two others injured when an explosion rocked their convoy north of Baghdad (search). Elsewhere in Iraq, another bomb exploded near an oil pipeline in northern Iraq while Iraqi police thwarted a potentially devastating car bomb attack in Baghdad.

The threat of another bombing is what tipped off the U.S. military to the massive weapons find.

An Iraqi citizen told the 1st Armored Division (search) about a homemade bomb attack that was supposed to take place Thursday.  After questioning the would-be attackers, American troops got information that led them to the weapons.

U.S. personnel from the 1st Armored Division along with those from 82nd Airborne (search) found the first weapons cache — some rockets, artillery rounds, mortars, blasting caps and C-4 explosives. They confiscated some of them and destroyed the rest.

But when they blew up the initial find, they discovered the larger supply hidden about 5 to 10 feet underground in tunnels and holes. The weapons were all kept next to a mosque.

Elsewhere, to the north in Mosul, the 101st Airborne Division opened fire at four Iraqis who attacked one of their compounds with rocket-propelled grenades. Two of the Iraqis were killed and a third wounded, the military said. The fourth escaped.

In the other stories out of Iraq Thursday that involved explosives:

— A convoy from the 4th Infantry Division was hit with an explosive near Baqubah, an area north of Baghdad. One unidentified soldier was killed and two others injured. The wounded soldiers were transported to the 21st Combat Support Hospital.

— Iraqi police thwarted what could have been a deadly car-bomb attack in Baghdad (search) and arrested a Syrian who confessed to having rigged the vehicle with explosives, Iraqi officials said.

Police found the explosives in a Toyota around 6 a.m. after receiving a tip from an informant. The suspect, believed to be in his early 20s, told police he had been given money to plant the explosives, according to Iraqi officials.

A second bomb fashioned out of an artillery or tank shell was found later outside the nearby An-Nahada secondary school and destroyed by U.S. troops.

— A bomb exploded near a pipeline in northern Iraq, killing two Iraqi Civil Defense Corps members and wounding 10 others, U.S. officials said.

The pipeline explosion in the north occurred south of Qayarrah (search), about 150 miles north of Baghdad. The Iraqi guards were helping secure pipelines that frequently have been the target of sabotage.

Sabotage to pipelines and the decayed state of Iraqi's infrastructure have slowed efforts to revive the country's giant oil industry, considered the key to rebuilding the economy.

American soldiers have been facing increasing guerrilla-style attacks with roadside bombs, small arms fire and rocket-propelled grenades.

U.S. officials have alleged that foreign fighters have been crossing the borders from neighboring Syria and Iran to join Saddam Hussein loyalists who are attacking coalition troops.

The incidents came as international representatives gathered in Madrid, Spain, for a donors' conference to raise money for Iraqi reconstruction.

Despite the approval last week of a new U.N. resolution setting out Iraq's future course, U.N. Secretary-General Kofi Annan (search) acknowledged that there are lingering divisions over Washington's role in running the civilian and military operations.

Bush administration officials have argued that they will not hand over operations to the Iraqis until elections are held and a constitution is drawn up.

Fox News' Molly Henneberg in Iraq and The Associated Press contributed to this report.