WASHINGTON (AFP) -- A U.S. investigation has found that Israel probably violated U.S. arms export agreements last year when it dropped U.S.-made cluster bombs among villages in Lebanon, the State Department said.

The investigation, summed up in a preliminary State Department report sent to Congress Monday, drew an immediate call from human rights activists for a cutoff of cluster munitions sales to the Jewish state.

"There were likely violations," State Department spokesman Sean McCormack told reporters of Israel's use of cluster bombs during a 34-day war against Lebanon's Hezbollah militia.

The cluster munitions spread bomblets over a wide area from a single bomb, rocket or artillery shell, and many of the submunitions fail to explode on impact.

More than 30 people have been killed and 180 others been injured in south Lebanon by ordnance left over from the war.

McCormack declined to provide further information about the report's findings or what end-use rules for cluster munitions Israel may have violated.

"Those parts of the agreements that we negotiate with a foreign government are classified, so we do not speak about them in public," he said.

He also stressed that the report transmitted Monday to the speaker of the House of Representatives and the chairman of the Senate Foreign Relations committee was preliminary.

"This is not a final judgment," he said.

But Human Rights Watch said the findings implicating Israel in the use of cluster bombs in civilian areas should be sufficient to end all sales of the weapons to Israel.

"We’ve investigated cluster munitions in Kosovo, Afghanistan, and Iraq, but we’ve never seen use of cluster munitions that was so extensive and dangerous to civilians," said Steve Goose, a spokesman for the group.

The group urged the U.S. government to end cluster bomb sales to Israel and demand detailed information regarding the quantities, types, and locations where U.S.-made cluster munitions were used in Lebanon.

If the violation of U.S. rules are confirmed, Israel could face sanctions, including a ban on future U.S. sales of cluster weapons to the Jewish state.

Israel was barred from buying cluster munitions for six years in the 1980s after the administration of president Ronald Reagan found it had made unauthorized use of the weapons during the 1982 invasion of Lebanon.

President George W. Bush has discretion under U.S. law over whether to impose the punitive measures on Israel, which receives some three billion dollars in U.S. military aid each year, the biggest amount of any U.S. ally.

McCormack declined to comment on possible sanctions that could be taken.

Israel now manufactures its own cluster munitions, so a renewal of the export ban would be largely of symbolic significance.

During the July 12-August 14 war against Hezbollah Israel dropped more than a million cluster bombs in southern Lebanon, according to the United Nations.

The war was ended by a UN-brokered ceasefire resolution that led to the deployment of Lebanese army troops and UN peacekeepers in south Lebanon along Israel's border -- an area that had long been under Hezbollah control.