A Palestinian pathologist who attended the autopsy of a Palestinian inmate who died in an Israeli prison over the weekend, determined on Sunday that the man had been tortured to death and had not died of a heart attack, as Israeli authorities had reported.

Kadoura Fares, a former PA minister and the head of the Palestinian prisoner’s club, was scheduled to hold a press conference reporting on Arafat Shalish Shahin Jaradat’s autopsy findings on Sunday evening.

Jaradat’s family members claimed they saw bloodstains on his body after they went to identify his remains at Israel’s main forensics institute on Sunday morning. They said they didn’t believe the official report that he apparently died of a heart attack.

Israel’s Justice Ministry issued a statement saying no visible signs were detected on Jaradat’s body, aside from those made by resuscitation efforts and a small graze on his chest.

“Two internal bleeds were detected, one on the shoulder and one on the right side of the chest. Two ribs were broken, which may indicate resuscitation attempts. The initial findings cannot determine the cause of death,” read the statement. “At this stage, until microscopic and toxicology reports are in, the cause of death cannot be tied to the autopsy findings.”

The autopsy’s official findings will be forwarded in two weeks to the PA and to Israel’s international criminal investigation unit. Custody of Jaradat’s body was handed over to his family after the inspection. His funeral will take place on Monday.

Palestinians on Sunday called for an international investigation of Israel’s treatment of detained Palestinians, after Jaradat’s death and a hunger strike by four other inmates sparked a week of West Bank protests.

Jaradat’s death raised new questions about Israel’s Shin Bet security service, which has been accused by rights groups of mistreating Palestinians during interrogation.

Palestinian officials and the detainee’s family alleged Jaradat was mistreated by the Shin Bet, saying he was healthy when he was arrested last week. Israeli officials said Jaradat died of a heart attack and denied he was beaten or subjected to any treatment that could have led to his death.

Several thousand Palestinian prisoners held by Israel observed a one-day fast Sunday to protest Jaradat’s death.

In all, Israel holds close to 4,600 Palestinians on a range of charges, from throwing stones at Israelis to involvement in deadly shooting and bombing attacks. Of the detainees, 159 are being held without charges or trial in so-called administrative detention.

The Shin Bet said Jaradat was arrested last Monday, after residents in his West Bank village of Si’ir said he was involved in a rock-throwing attack that injured an Israeli. Jaradat confessed to the charge, as well as to another West Bank rock-throwing incident last year, the Shin Bet said.

The agency said that during interrogation, he was examined several times by a doctor who detected no health problems. On Saturday, he was in his cell and felt unwell after lunch, the agency said. “Rescue services and a doctor were alerted and treated him, but they didn’t succeed in saving his life,” the statement said.

A Shin Bet spokesman, speaking on condition of anonymity in line with protocol, said Jaradat was not beaten during his interrogation, nor was he subjected to any treatment that could have affected his health. Jaradat was not on a hunger strike and died of an apparent heart attack, said Sivan Weizman of the Israel Prison Service.

Jaradat’s family and Palestinian officials alleged that he was mistreated during interrogation. Jaradat, father of a 4-year-old daughter and a 2-year-old son, worked as a gas station attendant. His wife, Dalal, is pregnant, relatives said.

Issa Karake, who handles prisoners’ issues in the Palestinian Authority, the self-rule government in the West Bank, said he holds Israel responsible for Jaradat’s death, alleging ill-treatment and medical negligence. Karake called for an independent international investigation of Israel’s treatment of Palestinian detainees.

The Israeli human rights group B’Tselem also demanded an investigation, including how Jaradat was questioned.

The agency routinely holds detainees in isolation for extended periods during interrogation, keeping them in cells that are lit round the clock and denying them access to lawyers, said Sarit Michaeli, a spokeswoman for the group.

Citing affidavits by detainees, she said that although physical mistreatment of detainees has dropped sharply in recent years, it has not disappeared. She also said detainees have filed some 700 complaints about mistreatment by Shin Bet agents over the past decade, but that none has led to a criminal investigation.

Jaradat’s death comes at a time of daily Palestinian demonstrations in support of prisoners, especially that of four hunger strikers. The health of one of the hunger strikers has deteriorated.

In recent days, protests often turned into violent clashes with soldiers.

Defense officials said Chief of Staff Lt. Gen. Benny Gantz convened top military officials Saturday night to discuss escalating tensions in the West Bank.