Only On 2: Family Believes 2-Year-Old Child Found Dead Inside Duffel Bag Is Their Kin

LOS ANGELES (CBSLA.com) —  The mystery surrounding the Whittier couple arrested at the Mexican border Tuesday with the  body of a 2-year-old girl in a duffel bag is only getting deeper.

Officials would not say how the girl was linked to the accused couple only to say the child was not the couple's biological child.

On Thursday, the family of a young woman stepped forward to say they believe they know who the little girl was.

Asking to not be identified because the investigation is on-going, the child's possible grandparents spoke to KCAL9's Tom Wait.

It's a story that is Only On 2.

Family members believe it's possible the body of the girl is related to them. He spoke with that family Thursday evening.

The family's saga started a year ago with a Facebook post in August 2015. In it, the grandfather says his daughter and granddaughter are missing. He identifies Mercy Becerra as the last one known to have seen his young relatives. Becerra is the same woman who was arrested Tuesday with Johnny Hartley at the border.

RELATED LINK: Police -- Whittier Couple Tried To Enter Mexico With Body Of 2-Year-Old In Duffel Bag

The family Wait talked to says they've talked extensively with detectives but have not received official confirmation the child is related to them.

They also say their young daughter is now safe with them at home but the granddaughter is still missing. It's not clear when their daughter returned. The connection between Becerra, Hartley and the daughter is also unclear.

Police served a search warrant in Whittier Wednesday. That's where they believe the little girl was killed. Becerra and Hartley lived in Whittier, according to investigators.

The couple was allegedly caught as they tried walking across the border into Mexico after authorities there X-rayed their bags.

Authorities said Becerra tried to make a run for it but was caught a short time later.