The Israel Defense Forces revealed on Tuesday that a huge amount of ammunition was stolen from a bunker at the Tze'elim training base in the Negev.
According to an initial probe, more than 20,000 assault rifle rounds were taken.
The Military Police opened an investigation in cooperation with the Israel Police.
In November, authorities arrested several suspects in a large-scale theft of ammunition from a military base on the Golan Heights.
Some 70,000 rounds of 5.56mm ammunition and 70 rifle grenades were stolen from the Tznobar training base near Katzrin.
The theft of firearms and ammunition from IDF bases has been a long-standing problem and forms a main source of weapons for the criminal underworld. The military has invested significant sums in installing new security measures around its facilities to prevent such incidents.
In October, the IDF said some 30,000 rounds of ammunition were stolen from the Sde Teyman air base near Beersheva.