Sirens sounded on Thursday in the southern Israeli district of Abu Qrenat, near the Dimona nuclear reactor, the Israeli army said without giving further details immediately.
A Reuters reporter about 90 km (56 miles) away from the site heard the sound of an explosion minutes before the army text message.
These siren alerts are usually triggered by rocket attacks.
Israeli Army Radio said that if this attack had taken place in the early hours of Thursday, its origin would not be immediately clear.
Abu Qrenat is deeper inside Israeli territory than the usual range of rockets by Palestinian militants in the Gaza Strip.
Israeli media have claimed for weeks that air defenses in the Dimona area and the Red Sea port of Eilat were being stepped up in anticipation of a possible long-range missile or drone attack by forces with support from Iran, perhaps from distant Yemen.
Tensions are high between Israel and Iran over Tehran’s nuclear program and a recent rise in sabotage attacks, some of which top enemies have blamed on each other.
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