A high-ranking official with the Islamic State militant group, also known as ISIS, who was believed to have lived in the U.S. for 10 years before joining the extremist fighters, may have been recently killed in Syria, counterterrorism officials said Wednesday. The claim came from jihadis themselves and was “far more reliable” than previous reports that Abu Muhammad Al-Amriki, who appeared in an ISIS video last February, had died, according to NBC News.

The latest report did not indicate how or when Al-Amriki may have died. Counterterrorism experts believed he might have migrated to the U.S. at an older age and spent some time there before joining the terror group and moving up its ranks. He appeared in a video in February wearing combat gear and holding what appeared to be a rifle. He spoke about his time in the U.S., however it was unclear whether he was a U.S. citizen.

Al-Amriki may have died during recent clashes in the northern Syrian town of Kobani along the Syrian-Turkish border, according to Mail Online. U.S. investigators have tried verifying the militants’ claims that Al-Amriki was dead. A report surfaced in October that Al-Amriki was “martyred” in Kobani, however an investigation revealed that he had been wounded, not killed.

U.S. officials have identified about a dozen Americans who have left the states in the past year to join ISIS, but some estimates have put the number much higher. The fear has been that American-born ISIS sympathizers could help the group implement attacks in the U.S. Last year, authorities discovered that Moner Mohammad Abusalha, the first U.S. citizen to carry out a suicide bombing in Syria, had returned to his home state of Florida after having trained with al Qaeda abroad, CBS News reported in August. Authorities believed that between 100 to 200 Americans like Abusalha have gone to Syria since 2011 and that some may have returned to the U.S.

In October, authorities revealed that terrorist group recruiters were attempting to indoctrinate young Somalis living in Minneapolis, Minnesota into their cause. The U.S. government estimated that since 2007, some 22 young Minnesotans have gone to Somalia to join an al Qaeda offshoot called al-Shabab.