(CNN) — Three women are believed to be missing in Mexico after they crossed the US border traveling from Texas to sell clothes at a flea market over two weeks ago, police told CNN on Saturday.

Marina Perez Rios, 48, her sister Martiza Trinidad Perez Rios, 47, and their friend Dora Alicia Cervantes Saenz, 53, crossed into Mexico on February 24, Roel Bermea, the Peñitas, Texas police chief, told CNN on Saturday.

The group was heading to the city of Montemorelos in the Mexican state of Nuevo León to sell clothes at a flea market, Bermea said. The flea market is about a 3-hour drive south from the US border.

The three women went missing one week before four Americans were kidnapped on March 3 in the Mexican border city of Matamoros, which is roughly 300 miles east of Montemorelos.

Two of the Americans, Shaeed Woodard and Zindell Brown, were killed and their bodies were delivered Thursday to US diplomatic authorities, according to a Mexican official. The two survivors — LaTavia Washington McGee and Eric Williams — returned to the US Tuesday to be treated in a hospital.

Six people in total have been arrested in connection to the violent March 3 abduction, including one on Tuesday, Tamaulipas Attorney General Irving Barrios Mojica said Friday.

An apology letter was issued Thursday by the Gulf Cartel, which is believed to be responsible for the kidnappings, and the group handed over five of its members to local authorities, according to images circulating online and a version of the letter obtained by CNN from an official familiar with the ongoing investigation.

US officials offer assistance

Marina’s husband spent all weekend calling the women. When he hadn’t heard from them by Monday, he turned to investigators for help, according to authorities.

The chief said the department confirmed the women crossed the border at the Anzalduas Port of Entry on February 24 in a 1995 Chevy Silverado.

Once the crossing was confirmed, the FBI was notified, Bermea said.

CNN has reached out to the FBI for comment but has not heard back.

It’s unclear whether Mexican authorities are investigating the matter.

A State Department spokesperson told CNN Saturday the department is “aware of reports of three U.S. citizens missing in Mexico.”

“The Department of State has no higher priority than the welfare and safety of U.S. citizens abroad. We stand ready to provide appropriate assistance to U.S. citizens in need and to their families,” the spokesperson said.

“When a U.S. citizen is missing, we work closely with local authorities as they carry out their search efforts, and we share information with families however we can,” the spokesperson said.

The chief urged the public to call local authorities with any information that could lead to the whereabouts of the women.

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