The Defense Ministry's Engineering and Construction Department and the Israel Prisons Service on Monday began to fill in and the underground spaces in the Gilboa Prison.
The work follows weeks of planning and preparations, after six convicted terrorists escaped the prison in September 2021.
Following the completion of the preparations, a line of tankers arrived Monday morning at the prison, pouring 1,200 cubic meters of special material into various spaces located ahead of time in both the prison's building and its infrastructure.
The material used to fill the spaces was prepared ahead of time by Defense Ministry engineers and construction experts.
The project, a joint undertaking by the Defense Ministry, Israel Prisons Service, and Public Security Ministry, is expected to last several weeks.