A former U.S. Customs inspector was arrested on Tuesday after he disguised himself as a postman and attempted to smuggle a Mexican woman into Texas on false documents, U.S. Customs and Border Protection authorities said.

According to department spokesman Rick Pauza, border inspectors in Del Rio, Texas, became suspicious when a 58-year old man wearing a U.S. Postal Service uniform tried to cross the U.S. border with a 38-year old Mexican woman.

The woman passenger said she was a U.S. citizen and showed a Texas birth certificate. However, the document turned out to be false and on interrogation, it turned out that the woman was, in fact, a Mexican citizen from Ciudad Acuna, in Mexico's northern Coahuila state.

Both were immediately arrested and taken into custody.

Pauza said it is unclear why the man was dressed in a postman's uniform or what is his relationship with the woman. However, it seems that the man had worked in Del Rio as a customs inspector.

It's fairly unique for officers to encounter someone wearing a U.S. Postal Service uniform when they are coming across the border from Mexico, so it certainly raised some eyebrows during the inspection process, Pauza told Reuters.

Port director Michael Perez said the border security will be beefed up to curb violations of immigration law.