Israel likely misused American-made cluster bombs in civilian areas of Lebanon during the war against Hezbollah last summer, the State Department said Monday.

Spokesman Sean McCormack said a preliminary report has been sent to Congress on a U.S. investigation of the issue. He did not provide details of the investigation.

The United Nations said last summer that unexploded cluster bombs — anti-personnel weapons that spray bomblets over a wide area — litter homes, gardens and highways in south Lebanon.

When Israel purchases cluster bombs and other lethal equipment from the United States, it must agree in writing to restrictions on their use.

The report, McCormack said, "is not a final judgment." He declined to speculate on what action may be taken against Israel if a violation is confirmed.

He said Israeli officials have been cooperative in providing information.

Israeli Foreign Ministry spokesman Mark Regev said Monday that "Israel takes the concerns raised by the U.S. extremely seriously" and had been as "forthcoming and transparent as possible."

"Israel is itself conducting an ongoing internal investigation as to the use of munitions during the Lebanon conflict," Regev said.

The U.N. Mine Action Coordination Center has said that it is not illegal to use the cluster bombs against soldiers or enemy fighters, but the Geneva Conventions bar their use in civilian areas.

Relief organizations and the U.N. mine office have reported finding evidence that Israel used three types of U.S.-made cluster bombs during the 34-day war with Hezbollah militants, during which both sides fired rockets into populated areas.

The U.N. mine office said in a report that it had found hundreds of bomblets of the types made by the United States among unexploded ordnance recovered in nearly 250 locations in southern Lebanon.

Israel also makes its own cluster munitions.

The Reagan administration imposed a six-year ban on cluster-weapon sales to Israel in 1982, after a congressional investigation found misuse of the weapon during Israel's war that year with Lebanon.

The Israeli army has said all weapons it uses "are legal under international law and their use conforms with international standards."

Cluster bombs are typically used against tanks and explode upon impact with steel. In the conflict in Lebanon, the shells were fired into urban and rural areas where Israel thought Hezbollah guerrillas might be hiding. Many hit the ground or pavement and did not explode.

Israel said it was forced to hit civilian targets in Lebanon because Hezbollah fighters were using villages as a base for rocket-launchers aimed at Israel. At least 850 Lebanese and 157 Israelis died in the fighting.

The Bush administration repeatedly warned Israel to avoid civilian casualties during the cross-border war, but refrained from direct criticism of Israeli tactics.