Gunmen who killed more than 30 Egyptian soldiers at a Sinai checkpoint this weekend were trained in the Gaza Strip and used stolen Israeli explosives and equipment, officials in Cairo told local media on Monday.

According to a report in the Egyptian El-Watan daily newspaper, initial investigation of the incident found that the attack was orchestrated by the Sinai-based Salafist extremist group Ansar Bayt al-Maqdis and that the bombers were trained in the Gaza Strip under Mumtaz Durmush, head of Gaza’s extremist Army of Islam terror group.

After infiltrating into the Sinai Peninsula via smuggling tunnels from Gaza, the bombers used stolen Israeli explosives and remote controlled devices to carry out the deadly attack, the pro-regime paper reported. It was not clear from the report how the Gaza-based terrorist groups obtained the Israeli equipment. Hamas is known to have amassed considerable amounts of Israeli army weaponry and equipment, some of which was used in the summer’s Israel-Hamas conflict.

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An earlier report in London-based Arabic newspaper Asharq Al-Awsat on Monday quoted an Egyptian Interior Ministry official saying that Palestinian militant groups were behind the attack. Maj. Gen. Sameeh Beshadi, former head of security in the Northern Sinai district, told the paper that there was “no doubt that Palestinian elements had taken part in the attacks” after slipping into Egypt from the Gaza Strip.

Hamas deputy politburo chief Mousa Abu Marzouk told Egyptian TV Monday that Hamas had no involvement in the attack.

“We regret hearing about any drop of blood spilled in Egypt or anywhere in the Arab world as such news is very painful,” Marzouk was quoted by Egypt’s RNN News saying, denying any connection between the Islamist group ruling Gaza and the Sinai attack.

Militants launched the complex assault on the checkpoint near the northern Sinai town of Sheikh Zuweid Friday. It involved a car bomb, rocket-propelled grenades and roadside bombs placed to target rescuers. At least 31 Egyptian soldiers were killed in the attack.

The bombing was one of the deadliest attacks targeting security forces since the army ousted president Mohammed Morsi last year. Egypt declared a three-month state of emergency in the Sinai Peninsula in response to the attack.

Egypt has been quick to point the finger of blame at Gaza, and on Sunday barred a Hamas delegation from crossing into Egypt ahead of planned indirect talks with Israel on a permanent Gaza ceasefire. Those talks were suspended.

Egypt’s deputy interior minister, Samih Bashadi, told Saudi-owned daily A-Sharq Al-Awsat that the bombing was carried out with the help of Palestinian operatives. Bashadi was elaborating on statements made earlier by Egyptian President Abdel-Fattah el-Sissi, who spoke of “foreign hands” involved in the attack.

Hamas’s interior ministry spokesman Iyad Al-Bozum asserted in comments posted on his ministry’s website Saturday that there were no more tunnels between Gaza and Sinai: “Tunnels between Gaza and Egypt no longer exist and have become a thing of the past since the Egyptian army shut them more than two years ago.”

But the Egyptian army seemed unconvinced. According to London-based Arab daily Al-Hayat, the army has begun a process of “temporary demographic redistribution” of the population living along the Egyptian side of the border, removing 680 families from their homes to create a buffer zone of 1.5 to 3 kilometers.

The Egyptian army has poured troops and armor into north Sinai to crush an insurgency that has raged since Morsi’s ouster. Earlier on Monday, Egyptian forces killed eight suspected jihadists in an unspecified location in the northern Sinai.

Jihadists, who have killed scores of security personnel, say their attacks are retaliation for the wide-scale government crackdown against Morsi’s supporters.

The crackdown has left at least 1,400 people dead and more than 15,000 jailed.

AFP contributed to this report.