A northern Arizona couple have been arrested on suspicion of child abuse after allegedly posting pictures on Facebook of their children bound with duct tape, KPNX reports.

The Coconino County Sheriff's Office says the 2-year-old and 10-month-old children were bound around their wrists and ankles and had their mouths closed with tape.

The sheriff's office says one child was hung upside down on an exercise machine, the Phoenix TV station reports.

KSAZ TV reports that Frankie and Kayla Almuina were arrested at their home in Williams, Ariz., after an anonymous tipster saw the photos on the mother's Facebook page and called the Arizona Child Abuse Hotline.

"They did indicate that they were simply joking, however it is apparent through the photographs that this was not a joke. The photos depicted the children's faces in sheer terror," Commander Rex Gilliland of the sheriff's office tells KSZA. "Clearly you can't tape another person's hands and mouth shut. Especially small children. It is clearly child abuse and they were charged appropriately."

The children were placed in the custody of relatives while the investigation continues, KSAZ reports.