Gilboa Prison in Israel's North declared a state of emergency on Monday evening after guards found what they thought was a pistol near the observation tower but upon further inspection it turned out to be a fake weapon made of sponge, Israeli media reported.

Police have begun investigating the incident, including how and why the sponge weapon got to be where it was found.

The incident comes following the recent escape of six Palestinian security inmates from the prison last week. They managed to tunnel out of what had been regarded the country's most secure prison, according to Maariv. In the week since the escape, four of the fugitives, including high-profile prisoner Zakaria Zubeidi, have been caught.

The escape has caused many to question the security and competence of the prison system and this was further highlighted after investigations found that not all observation towers at the prison were staffed due to manpower shortages. These towers would instead remotely monitor the area with video images from security cameras being fed to a control room, although the guards on duty at the time apparently did not notice anything suspicious.