Israel’s defense establishment has strengthened convictions that some of the hundreds of wildfires burning across Israel since Wednesday have been caused by systematic arson, in some bases, by Arab terrorists with nationalistic backgrounds.

The Shin Bet security service confirmed that it was investigating the conflagrations that have forced tens of thousands to evacuate, but said it was too soon to reach any conclusions.

More than 220 fires have erupted throughout central and northern Israel, forcing the evacuation of thousands of Israelis from their homes across the country as flames encroached on residential areas, major roadways, and vital infrastructure, including installations of the Israel Electric Company.

Some 250 Israeli firefighters and soldiers have been working for days to extinguish fires, which have ignited in areas surrounding Beit Shemesh, Modi’in, and Jerusalem, as well as in Haifa, Hadera, Zichron Yaakov, Umm al-Fahm, Lachish, Nesher, the  Gush Etzion, and outside the northern town of Kfar Vradim.

Firefighting efforts on Thursday were concentrated in the northern coastal city of Haifa, where Israel’s Fire Authority ordered tens of thousands of residents to evacuate.

Turkey, Russia, Croatia, Italy, Greece, and Cyprus will send ten firefighting planes and personnel to assist in battling the flames. Four such planes, three from Greece and one from Cyprus, have already arrived and are operational in Haifa, dumping tons of flame retardant on flames fed by high winds and unseasonably dry weather conditions.

Early security assessments have suggested many of the fires were set intentionally by Arab terrorists, prompting Public Security Minister Gilad Erdan and Police Chief Ronnie Alshich have moved to boost security as deterrence to potential terrorists, ordering hundreds of police officers and soldiers to open spaces near villages and towns along Judea, Samaria and Gush Etzion.