FRANKLIN, Ind. -- The mother and grandmother of three missing children are pleading for their safe return, fearing the children might have been taken to Mexico.

Leeanna Cummins wondered if she will ever see her three daughters, Sierra, 7, Jasmine, 2, and Jaden, 16 months, again.

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Images: Missing Children

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Johnson County authorities said they think the children could be in Mexico, with the paternal grandmother of the two youngest children, Laura Vivas, and her boyfriend, Javier Hernandez.

"There was a phone call or a voicemail left on one of the daughter's phones that she was in Mexico, the kids were fine and that they wouldn't be returning," Cummins said.

Cummins' mother, Cindy Rippy, said her granddaughters are her life and that she would be willing to go to Mexico herself to look for the children, if she knew where to start, 6News' Tanya Spencer reported.

"When somebody goes and takes your family away from you and to … possibly a country that you don't know nothing about, it's hard," Rippy said.

Cummins and Rippy said they worry for the girls' safety and fear that especially the oldest girl might be scared.

"She has to be wondering, 'Why am I here?" Rippy said. "How's my grandma? How's my mommy?"

The father of the two youngest children, Vivas' son, was released from prison this week.

Vivas and Hernandez are believed to be in a red Ford extended cab pickup truck.