Upon the arrival of Islam, Khaybar was a Jewish town inhabited by as many as eight Arab Jewish tribes. The fortress of Khaybar is often referred to as the Fortress of the Jews, while an ancient Jewish cemetery exists somewhere in the vicinity. Some of these tribes are thought to have settled the area as early as the 6th century BC, but others probably arrived in the 1st century AD following the Great Jewish Revolt against the Romans, while some may have been Arab converts from the 6th century AD Yemeni-Jewish kingdom of Dhu Nuwas. Three of these tribes resettled from Medina after their expulsion following friction with the Prophet Mohammed, only to be once again under his authority when he conquered Khaybar in 629 AD. The other five tribes made a truce with the Prophet and all tribes were allowed to continue to live in Khaybar. In 642 AD, after Mohammed's death, Caliph Omar forced many of the Jews of Khaybar to leave and resettle in Jericho and other parts of the Levant and Iraq, but a large number did stay in Khaybar, mainly those from the five tribes with whom the Prophet had made a truce. It is unclear how long thereafter these tribes remained in Khaybar, but their population likely dwindled over time. Historic evidence does confirm Jewish presence as late as the 12th century, and many whisper that a small number of Jewish tribes continue to live in Arabia to the present day! This is unlikely, but if true, it is unclear whether or not they would be in Khaybar, or more likely near the Yemeni border in the Asir region down south. Understandably, the Saudi government would want to keep such a fact a secret (if this is even remotely true), not only to protect any remaining Jewish citizens, but also to avoid an Israeli-style "airlift" such as that which occurred in Yemen in 1949.
Saudi Arabia seems in no rush to promote tourism or archaeological excavation to Khaybar likely because of its Jewish roots. This is in part politically motivated, perhaps in fear of recalling the "Greater Israel" dream of some early Zionists, who had hoped to create a Jewish state from the Nile to the Euphrates, including northwestern Arabia. Khaybar could have been part of it because of its ancient Jewish history, and any archaeological finds could ignite Israeli claims over the area. Although such Israeli-Zionist dreams may be inconceivable today and those fears may seem unfounded, this was not the case in the eyes of Arabs immediately following the 1967 war when Israel captured vast Arab lands. Still, the area around the Fortress is fenced off with a sign noting that it is reserved for archaeological excavation. Perhaps in the near future work to uncover its history will begin.