The Code Red alert, which warns of incoming rockets or missiles from the Gaza Strip, was heard in several southern communities late Sunday.
The alarm was sounded in areas surrounding the Ashkelon Regional Council. IDF forces were searching the area for the site of the Kassam landing, which according to initial reports, may have landed in open territory.
Earlier this month, three Kassam rockets were fired from the Gaza Strip at Israeli territory, all landing in open Gazan territory.
The rocket fire followed a series of unsuccessful attacks on Israel in past few months.
Last month, Israel and Gaza marked the one-year anniversary since Operation Pillar of Defense, an eight-day offensive launched by Israel to stem rocket fire from Gaza.