Iranian authorities have arrested 15 Christian converts and subjected them to harsh and inhumane interrogations.

The Farsi Christian News Network reported the group was arrested in July. They were taken into custody while traveling through the city of Masshad.

Although Masshad is a center of pilgrimage and religious training for Shiite Muslims, the network reported converts to Christianity are on the rise there.

Thirteen of the believers were freed after posting bail. Two remain in custody.