The search for three U.S. soldiers believed captured by Al Qaeda terrorists intensified Monday after commanders obtained what they called a flood of new intelligence.

Col. Mike Kershaw of the 10th Mountain Division, the army unit leading the search, said the discovery of a small piece of a U.S. Army uniform believed to belong to one of the missing GIs had raised hopes that the soldiers would be found alive.

Kershaw said the physical evidence, which was found in the 135-square-mile area south of Baghdad that troops have been searching since the soldiers disappeared, had not been discounted by forensics.

U.S. military sources also said several individuals detained in the searches had provided new information regarding the ambush and abduction during interrogations.

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The new information had led to five specific search operations on Monday as thousands of other soldiers combed through fields and questioned local residents.

The three 10th Mountain Division soldiers have been missing since May 12, when insurgents carried out a predawn ambush that left four other U.S. troops dead.

Meanwhile, a group of gunmen in two cars attacked a minibus heading to Baghdad from a Shiite town north of the capital, killing seven passengers including a child, police said.

The minibus attack underscored the sectarian violence and instability that continues to plague Diyala province north of Baghdad despite the three-month-old security crackdown in Baghdad and the surrounding areas.

The bus, which left the town of Khalis, was driving near the violence-wracked city of Baqouba, 35 miles northeast of Baghdad, about 11:30 a.m. when it was ambushed outside the town of Hibhib, police said.

In western Baghdad, a roadside bomb detonated near a group of Iraqi soldiers patrolling the Sunni-dominated Adil neighborhood, killing three of the soldiers and injuring two others.

The stepped-up U.S. and Iraqi patrols of the capital during the crackdown have left the troops more vulnerable to attack by insurgents, military officials say.

The U.S. military reported Sunday that six U.S. soldiers on patrol in Baghdad were killed in a roadside bombing along with their interpreter on Saturday. A seventh soldier died in a blast Saturday in Diwaniya, a mostly Shiite city 80 miles south of the capital, where radical Shiite militias operate.

Also on Sunday, two U.S. Republican senators at an international conference hosted by the Geneva-based World Economic Forum in Jordan said that the U.S. has evidence Iran sent weapons and trainers to instruct militants in Iraq to carry out terror attacks.

Republican Sen. Orrin Hatch told a panel discussion on Iraq's future that during a trip last week to Iraq, he saw "evidence that Iran was supplying weapons and bomb-making components to Iraqi terrorists."

A former Iranian government official, who was on the same panel, denied the claims.

"Iraq is already so full of arms that it doesn't need arms from Iran," said hard-liner Mohammed J.A. Larijani, a former deputy foreign minister and brother to Iran's top nuclear negotiator, Ali Larijani.

But Republican Sen. Gordon Smith told the panel he saw "confiscated Iranian weapons" and captured Iranians who confessed to a mission to train Iraqi extremists in military tactics.

In recent months, U.S. officials also have stepped up pressure on Iraq's religiously and ethnically based parties to reach agreements on a range of political and economic initiatives to encourage national reconciliation and bring an end to the fighting.

Progress in meeting those benchmarks is considered crucial to continued U.S. support for Prime Minister Nouri al-Maliki's government at a time when Democrats in Congress are pressing for an end to the war. Those benchmarks include enactment of a new law to manage the country's vast oil wealth and distribute revenues among the various groups.

But prospects for quick approval received a setback Sunday when the country's Sunni vice president told reporters in Jordan that the proposed legislation gives too many concessions to foreign oil companies.

"We disagree with the production sharing agreement," Tariq al-Hashemi told reporters on the sidelines of the Jordan conference. "We want foreign oil companies, and we have to lure them into Iraq to learn from their expertise and acquire their technology, but we shouldn't give them big privileges."

The bill also faces opposition from the Kurds, who have demanded greater control of oil fields in Kurdish areas. Kurdish parties control 58 of the 275 parliament seats.

Iraq's Cabinet signed off on the oil bill in February and sent it to parliament, a move that the Bush administration hailed as a major sign of political progress in Iraq. But parliament has yet to consider the legislation.

Al-Hashemi is among three leaders of a Sunni bloc that controls 44 seats. Together, the Kurds and the Sunnis have enough legislative muscle to delay passage of the measure, which is likely to draw opposition from some Shiite lawmakers, too.

In another political setback, the leader of Iraq's largest Shiite party, Abdul-Aziz al-Hakim, was diagnosed with lung cancer and headed to Iran for treatment, party officials said Sunday. Al-Hakim's absence is likely to create disarray in his Supreme Islamic Council in Iraq — a Shiite party the U.S. is counting on to push through benchmark reforms.

News of al-Hakim's diagnosis came only hours after another top Iraqi leader, President Jalal Talabani, flew to the U.S. for a medical checkup. The 73-year-old Kurdish leader was hospitalized in Jordan three months ago after collapsing.

Talabani has played an important role in trying to bridge the gap between Sunni Arabs and Shiites, and his absence is also likely to complicate efforts to forge national unity.

FOX News' Courtney Kealy and The Associated Press contributed to this report.

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