PEÑITAS, Texas (AP) — The daughter of one of two sisters from Texas who went missing in Mexico along with their friend three weeks ago while traveling to a flea market says she hasn’t lost hope that they’ll be located.

“We are waiting for them to come back home,” Maria Guadalupe Ramirez, 27, told KRGV-TV in Weslaco.

The FBI said in a statement Thursday that it was unable to comment on the investigation but said the agency “relentlessly pursues all options when it comes to protecting the American people, and this doesn’t change when they are endangered across the border.”

The three women — Ramirez’s mother, Marina Perez Rios, 48; Ramirez’s aunt, Maritza Trinidad Perez Rios, 47; and their friend, Dora Alicia Cervantes Saenz, 53 — were headed to a flea market to sell clothes in the Mexican city of Montemorelos in the state of Nuevo Leon. The state prosecutor’s office in Nuevo Leon has said it is investigating the women’s disappearance.

The sisters live in Peñitas, a small Texas border city near McAllen, and are legal U.S. residents, while their friend, Saenz, lives in Mexico, KRGV reported.

Ramirez, who spoke to KRGV on Tuesday, said she’s been in contact with Mexican authorities. She told the TV station that her mother and aunt, who grew up in Nuevo Leon, have made the trip several times to the market.

“They had fun going out there, meeting new people,” Ramirez told KRGV.

Ramirez told The Monitor in McAllen that she last spoke to her mother Feb. 25, the day after her mother and aunt crossed the border into Mexico.

Another case of Americans who went missing in Mexico received an avalanche of attention earlier this month when their March 3 resolved in a matter of days when the four were found in a wooden shack. Two were alive and two were dead.

The massive search for the four kidnapped Americans involved squads of Mexican soldiers and National Guard troops. But for most of the 112,000 Mexicans missing nationwide, the only ones looking for them are their desperate relatives.