(NewsNation) — As Americans celebrated Mother’s Day on Sunday, one Southern California family marked another holiday without their matriarch, who was kidnapped in Mexico over a year ago and remains missing.

Maria del Carmen Lopez, a 63-year-old U.S. citizen and grandmother of 19, was taken by armed men from her home in Pueblo Nuevo, Mexico, on Feb. 9, 2023. Her daughter Zonia Lopez spent Sunday putting up missing person posters in the area, now over 400 days since her mother’s abduction.

The kidnappers initially contacted the Lopez family demanding an unreasonable ransom payment for Maria’s release, the family said. Mexican authorities arrested two men linked to a local kidnapping ring shortly after, but no new information about Maria emerged.

The FBI requested permission from Mexican officials to join the investigation within Mexico but was denied, according to Elizabeth Lopez, another daughter.

“The FBI has requested permission to go into Colima to take over this case and see what these men have to say, but the state will not grant them permission to go in and investigate themselves,” she said, referring to the western Mexican state where her mother was taken.

With the criminal probe stalled, the California family has channeled their despair into activism to draw more attention and resources to the case. They launched a website called Justice4Carmen with a petition urging U.S. lawmakers to assist in securing her safe return.

“If anybody can go into that website … sign the petition, it takes literally a minute or two to sign. But it does make a big difference to us,” Elizabeth Lopez said. “That’s the goal of the petition.”

As another Mother’s Day passed, the family refused to give up seeking answers about the beloved matriarch’s fate, clinging to hopes she remains alive over a year after her kidnapping.