The bodies of 42 people, including women and children, have been found in a mass grave in the ancient city of Palmyra by Syrian troops, Agence France-Presse reported Saturday.

The grave was found on the northeastern edge of the city, which was recaptured by Syrian forces last Sunday from the Islamic State group after a monthlong battle. AFP reported some of the victims had been beheaded. A military source told AFP the victims were officers, soldiers and members of their families. Of the total, 24 were civilians, AFP reported.

“They were executed either by beheading or by shooting,” the source told AFP.

Syria’s official Syrian-Arab News Agency first reported the find Friday.

The Inter-Asian News Service said soldiers pulled 40 bodies out during combing operations in the Nasakin al-Jahzia neighborhood. IANS said all of the bodies were women and children. Some of the victims had been tortured before they were killed, IANS said.

The bodies have been taken to a military hospital in Homs for identification.

Recovery efforts were slowed by land mines and other explosives planted by the terrorist group, aka ISIS, before it fled. Iran’s semi-official Press TV reported Syrian soldiers have detonated some 500 mines.

“They planted two to three mines together every 100 meters. The mines were laid to impede the advance of the government force,” a Syrian army commander identified only as Munzer told Press TV.

The Syrian Observatory for Human Rights, based in the U.K., said ISIS killed 280 people while it was in control of the city, which hosts a number of World Heritage sites heavily damaged during the occupation. IANS said ISIS killed 400 people in Palmyra last May, mostly women, children and the elderly, when the terrorist group first overran the city.

Syrian forces, backed by Russian air support, plan to use Palmyra as a base to further rout ISIS, which has occupied large swaths of Iraq and Syria. The BBC said ISIS-held towns of Qaryatain, southeast of Palmyra, and Sukhnah, northeast of the city, are among the targets.

Syria’s civil war began in 2011 during the so-called Arab Spring. The Syrian Center for Policy Research has estimated more than 470,000 people have died in the conflict, with millions more displaced.