British police are investigating what has happened to three sisters and their nine children who failed to return from an Islamic pilgrimage. They are feared to have traveled to join extremists in Syria.

Police on Tuesday are trying to establish the whereabouts of the Dawood family, from Bradford, England, who disappeared after going to Saudi Arabia. Their disappearance comes amid questions about how to tackle the radicalization of young people attracted to the Islamic State group's slick propaganda.

Khadija, Sugra and Zohra Dawood, all in their 30s, travelled to Medina with their children, aged 3 to 15, on May 28. They were due to return June 11, but broke off all contact June 9.

A lawyer acting for the fathers says it's possible the group traveled to Syria via Turkey.