Most of the right-wing activists who vandalized the Ephraim Brigade's base two weeks ago were students at Jerusalem's Mercaz Harav Yeshiva, police have discovered.

In a related development, the Shin Bet security service has recommended putting at least three right-wing extremists in administrative detention in response to the recent escalation in violent attacks on both Palestinians and Israel Defense Forces soldiers. Prime Minister Benjamin Netanyahu urged the security services to make use of such detentions two weeks ago, after right-wing extremists perpetrated a spate of attacks within a single 24-hour period, including the one on the Ephraim Brigade base.

According to the police, that incident began on Monday afternoon, December 12, when calls went out to right-wing activists nationwide to go to the northern West Bank to protest the planned demolition of an illegal settlement outpost, expected to be either Mitzpeh Yitzhar or Ramat Gilad. Three well-known activists - Effi Chaikin, Eliav Eliyahu and Meir Ettinger, all of whom were barred from entering the West Bank under an administrative order issued by the army and were therefore living temporarily in Jerusalem - then began organizing a group of youths to join the protest.

A bus was rented, though police aren't yet sure by whom, and told to come to Mercaz Harav, a leading religious Zionist yeshiva that has been a driving force behind the settlement movement. There, some 40 people got on, most of them students at the yeshiva.

En route to the West Bank, the bus was told to stop and several tires were loaded on. The driver later told the police that "a man without a beard" was in charge of the passengers.

At the entrance to the base, two of the passengers bought containers of gasoline from a nearby gas station. Police have seized the footage from the gas station's security cameras as evidence. The passengers then burned the tires they had brought at the entrance to the base.

At some point, some of them also broke into the base. Most stood at the entrance and shouted "Jews don't expel Jews." But others entered the base's parking lot and vandalized cars belonging to brigade officers.

Two days later, on December 14, police raided the three activists' apartment, which is located near the yeshiva. On Tuesday, their remands were extended for the fifth time, until Sunday.

Cell phone records indicate that the three were in contact with the busload of students who went to the West Bank, but it's not yet clear whether the content of their calls provides any evidence that they committed a crime. Police also found aerial photographs, maps and indications that they had been keeping track of IDF forces, as well as seditious articles, in their apartment and on their computers.

This week, police arrested O., a West Bank resident who studies at Mercaz Harav, on suspicion that he helped organize the bus and then participated in the riots. On Monday, police had the bus driver and an IDF officer review a photograph line-up, and both said they were "80 percent sure" that O. was present near the Ephraim Brigade base that night.

O. was remanded until tomorrow, but Judge Avital Chen hinted clearly that he would not extend the remand unless police produce more evidence by then. O. denies the allegations.

Police sources said they expect to arrest several of the other passengers on the bus in the coming days. They said they have a list of most of the passengers, but will focus on trying to arrest the ringleaders.

In contrast, however, police have as yet made no progress in determining who attacked the Ephraim Brigade's commander and deputy commander on Route 55 that same night.

Meanwhile, the Shin Bet is seeking administrative detention orders against three right-wing extremists whom it considers principally responsible for the recent escalation in the West Bank. It has prepared intelligence files on all three and sent them to the prosecution for legal scrutiny; if the prosecution approves, they will be sent on to Defense Minister Ehud Barak, who must sign off on the orders. The orders must also be approved by a district court.

Both Barak's office and the Shin Bet declined comment.

Legally, there is no barrier to putting either Jews or Arabs in administrative detention, and the government has made relatively widespread use of this tool against Jews twice in the past: after Baruch Goldstein murdered 29 Arab worshipers at the Tomb of the Patriarchs in Hebron in 1994, and during the period of the disengagement from the Gaza Strip in 2005. Since then, however, only a handful of Jews have been put in administrative detention. The last such case was two years ago, after intelligence information indicated that a particular extremist had spoken in favor of killing policemen. But he was ultimately released in exchange for leaving the country for a time.

Read this article in Hebrew