The July 31 attack on the Dawabsheh family's house in Duma, a village near the city of Nablus, burned 18-month-old Ali to death. His father Saad, 32, and mother Reham, 26, succumbed to their wounds weeks later. Ali's brother Ahmed, 4, is being treated in an Israeli hospital for burns covering 60 percent of his body.

The perpetrators scrawled the Star of David above the word “revenge” on an outside wall of the house, leading authorities to believe the incident to have been a “price tag” attack. Jewish settlers have carried out such assaults on Palestinians and their property in retribution for Israeli government actions perceived as siding with Palestinians over Israeli settlers.

All settlements in the West Bank and East Jerusalem are illegal under international law, and are widely seen as an obstacle to peace between Israelis and Palestinians.

Israeli Prime Minister Benjamin Netanyahu has condemned the Duma attack and vowed swift action to bring the perpetrators to justice. "This is a terrorist attack. Israel takes firm action against terrorism, no matter who its perpetrators are," he said in July.

Israeli authorities questioned several suspects, but released them due to what they said was a lack of evidence. Three Israelis who belong to far-right groups were also apprehended, but for unrelated reasons, and were held in administrative detention — a controversial form of imprisonment, usually reserved for Palestinians, in which suspects are detained indefinitely without charge, trial or access to counsel if they are deemed a security threat.

Ya'alon said Thursday that the Duma attack perpetrators were also being held in administrative detention, but it was not clear if they are the same as those previously detained.

Similar attacks by right-wing settlers have targeted Palestinian mosques, churches and farms.

On Wednesday, Israelis from the settlement of Yizhar set fire to dozens of olive trees in the village of Burin, south of Nablus, in sight of Israeli soldiers, Palestinian media outlet Ma’an News reported.

Since the start of this year, Palestinians have suffered 50 casualty incidents and 91 property damage incidents due to settler-related violence in the West Bank and East Jerusalem, according to U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

Israel has promised to crack down on such attacks, though only a handful of indictments have been handed down.