(CNN) -- An Arizona couple remained in custody Saturday morning after police said they duct taped the wrists, ankles and mouths of their two children and posted the photos on Facebook.
The children in the photo were a 2-year-old boy and a 10-month old girl, according to a Coconino County Sheriff's incident report. One showed the boy hanging upside down by his ankles from a weight machine.
A friend who saw the photos called the state child abuse hotline Wednesday, prompting the sheriff's office to arrest the parents, Frankie Almuina, 20, and Kayla Almuina, 19.
The mother told investigators the photos were "all in fun" and that the children were unharmed and were smiling afterward.
She also showed the reporting officer, Sgt. Michael Curtis, several other photographs on her cell phone that showed the little girl similarly bound.
"They indicated they did this as a joke," county Sheriff's Commander Rex Gilliland told CNN affiliate KTVK. "But there was fear on the children's faces in the pictures."
"I don't know how anybody can rationalize taping a child's mouth and then binding their hands and feet," he added.
Police would not release the photos, saying they were too disturbing.
In her Facebook page, Kayla Almuina describes herself as a "stay and home mommy and wife" and jokes she studied at "harvard :)! jk."
She told investigators that the reason the girl was appeared to be crying in the cell phone photos was because she had received some shots that day.
Authorities placed the children in the custody of their grandparents.
The parents, charged with two counts of child abuse each, remain in jail with bond for each set around $25,000.
Last week, a 21-year-old Chicago man was charged with aggravated domestic battery after he posted a picture of his 22-month-old daughter bound with painter's tape across her mouth, her wrists and ankles.
The caption on the Facebook photo read: "This is wut happens wen my baby hits me back. ; )."