U.S. Customs and Border Protection officials say 37-year-old Maria Veronica Martinez, of Fresno, was crossing into Arizona at the Nogales port Monday when her sedan was pulled over for an additional inspection.
They say she was searched after a drug dog alerted CBP agents to her.
Agents reported finding one package of heroin wrapped around her midriff with duct tape.
They say heroin had an estimated street value of $123,000.
The drugs and vehicle were seized and Martinez was turned over to U.S. Immigration and Customs Enforcement's Homeland Security Investigations.
Authorities didn't immediately know Wednesday whether Martinez had a lawyer yet.