BEIRUT -- The United Nations Interim Force in Lebanon (UNIFIL) said on Monday that Israeli aircraft dropped a chemical substance near the border, calling the move a violation of UN resolutions that "severely disrupted" its operations.

The UNIFIL said the Israeli military gave advance notice Sunday morning that it would release the substance. While Israel described the material as non-toxic and warned peacekeepers to stay indoors, UNIFIL said the incident forced it to cancel more than a dozen activities. Operations along a third of the "Blue Line" -- the unofficial border between the two countries -- were halted for over nine hours.

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UNIFIL labeled the action "unacceptable", noting it hindered the mission's mandate and could pose health risks to both peacekeepers and civilians. Peacekeepers assisted Lebanese forces in collecting samples of the substance to test for toxicity.

The UN also raised concerns about the long-term impact on local farmland and the ability of displaced residents to return home.

Israeli overflights have long been a point of contention. UNIFIL reiterated that such actions breach UN Security Council Resolution 1701. That 2006 agreement ended a monthlong war between Israel and Hezbollah, calling for a demilitarized zone in southern Lebanon patrolled only by the Lebanese army and UN peacekeepers.

The mission urged Israel to stop the activity to help maintain stability in the region.