The suspected ringleader of a terror cell accused of carrying out deadly bombing attack last month was hospitalized Saturday in critical condition after an interrogation by the Shin Bet security service, his attorneys said.

On Saturday night, the Shin Bet revealed that it had arrested three Palestinian men suspected of carrying out the August 23 attack at a natural spring in the West Bank, killing Israeli Rina Shnerb, 17, and seriously injuring her father and brother.

This cell was allegedly led by Samer Mina Salim Arbid, 44, who has a history of involvement in terrorist activities with the Popular Front for the Liberation of Palestine terror group, according to Israeli authorities.

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Arbid was arrested earlier this month and then released due to lack of evidence. He was picked up again on Wednesday.

According to the Haaretz newspaper, which first reported on him being hospitalized, the Shin Bet was given legal permission to employ “extraordinary measures” in its interrogation of Arbid. Such measures can include forcing prisoners into uncomfortable positions, sleep deprivation, shackling and subjecting prisoners to extreme temperatures.

This is typically allowed in cases of a “ticking time bomb,” where there is concern that the suspect could provide security forces with information that could prevent an imminent attack.

The Shin Bet said the cell was planning additional attacks when the suspects were arrested, including shootings and kidnappings. During the arrest raids, security forces also found and safely detonated an improvised explosive device that the group had made.

Arbid was taken to Jerusalem’s Hadassah Hospital Mount Scopus in critical condition after he apparently suffered a heart-related problem during the interrogation.

His attorneys said he had been healthy when he was arrested, Haaretz reported.

“Samer Arbid was severely tortured by Israeli interrogators. He was transferred to the hospital unconscious and suffers from several fractures,” his lawyers said said in a statement released by the Addameer Foundation, a Palestinian legal organization that often represents terror suspects.

MK Ofer Cassif (Joint List) accused the Shin Bet of torturing Arbid. “The use of torture is terrible and not allowed, no matter what it is directed against. We cannot accept the torture of the suspect in the murder of Rina Shnerb, as vile as his actions were,” he wrote on Twitter.

The Shin Bet confirmed only that Arbid had been taken to the hospital.

“During his interrogation, the leader of the terror cell that carried out the IED attack… in which Rina Shnerb was killed said he did not feel well. In accordance with protocol, he was taken for medical checks and treatment at the hospital. The investigation into the cell is ongoing,” the security service said in a statement.

On August 23, an IED that had been planted next to the Bubin natural spring in the central West Bank, near the Dolev settlement, was triggered by terrorists as the Shnerb family from the central Israeli town of Lod visited the site. Rina Shnerb was declared dead at the scene and her father Eitan and brother Dvir, 19 were taken to a hospital in Jerusalem after being wounded by the blast.

“Arbid led the cell, prepared the IED and set it off the moment he saw the Shnerb family reach the spring,” the Shin Bet said in a statement Saturday night.

Qassem a-Karim Rajah Shibli, 25, is suspected of manufacturing the explosive material used to make the bomb, helping put it together and setting it off, according to the security service.

Yasan Hasin Hasni Majamas, 25, is believed to have been involved in the planning and execution of the attack, the Shin Bet said.

Both Shibli and Majamas have served time in Israeli prisons for their involvement in terrorist activities, the security service said.

In addition to these three, who are believed to have carried out the attack, the Shin Bet said it arrested a fourth man — Nizam Sami Yousef Ulad Mahmoud, 21 — who is suspected of being a member of Arbid’s cell. He is a member of the PFLP’s student group at Bir Zeit University in the West Bank.

The Shin Bet said it was still looking for additional members of the terror cell.