Turkey captured the elder sister of the slain leader of the Islamic State terrorist group in a northwestern Syria trailer park on Monday, according to a senior Turkish official, who called the arrest the first step in an intelligence “gold mine.”

The 65-year-old, named as Rasmiya Awad, was detained in a raid near the town of Azaz, officials said. Turkish officials, cited by several media outlets, are confident the arrest could yield valuable intelligence about Islamic State and its operations.

The official said the sister was with her husband, daughter-in-law and five children. The adults are being interrogated, he said, speaking on condition of anonymity in line with government protocol.

One Turkish official told Reuters news agency the arrest of Baghdadi’s older sister may help shed light on “the inner workings” of Islamic State.

Abu Bakr al-Baghdadi was killed during a raid by U.S. special forces on his compound in north-west Syria last month.

Turkish President Tayyip Erdogan’s communications director said the woman’s capture was evidence of Turkey’s determination to fight against Islamic State.

“The arrest of al-Baghdadi’s sister is yet another example of the success of our counter-terrorism operations,” Fahrettin Altun wrote on Twitter early on Tuesday.

“Much dark propaganda against Turkey has been circulating to raise doubts about our resolve against Daesh,” he wrote, using another name for Islamic State.

“Our strong counter-terrorism cooperation with like-minded partners can never be questioned.”