The Christians on Facebook name was changed to "La ilaha illallahu Muhammadur Rasulullah", which means "There is no god but Allah; Muhammad is the messenger of Allah," reports TG Daily.
The group's name changed several times thereafter and by the end of the day read, "There is No God but ALLAH; Muhammad is the messenger of Allah."
The hackers also changed the group's photo to one of "Shahadah", or Islam's declaration of faith.
A Google snapshot taken of the Facebook group page last week showed that the original photo was a cross. In the group's description, the creators of Christians on Facebook included several Bible verses and an invitation for Christians from any denomination to join.
The description also stated, "Non christians too are welcomed with open arms."
Following the hack, the description now displays posts explaining the basic tenets of Islam.
Applications that allowed members of the group to participate in discussion boards, write on the group's wall, post photos and link videos have all been deactivated.
Additionally, Facebook users who were listed as the group's Admin have been replaced with a user going by the name of "Sarah Ha", which appears to reference Sarah and Hagar of the Bible.
In the biblical Genesis account, Abraham fathered Isaac with his wife Sarah, and Ishmael with Sarah's maidservant Hagar. Isaac was considered the son born of "promise" and Ishmael was considered the son born of a slave woman. Judaism and Christianity is thought to have descended from Isaac whereas Islam is associated with Ishmael.
The hacking incident prompted thousands of Facebook users to leave the group.
According TG Daily, the membership went from 327,400 at the time of the attack down to around 324,000 by Tuesday evening.