Two men are facing criminal charges after authorities discovered that they had a backpack full of heroin during a traffic stop.
The drug seizure happened on the 100 block of East Polk Avenue on Tuesday.
A Hidalgo County Pct. 4 deputy constable pulled over a 1995 Toyota Corolla for a routine traffic stop.
Hidalgo County High Intensity Drug Trafficking Area (HIDTA) task force officials reported that a K-9 officer was called to the scene.
The K-9 officer allegedly alerted the deputy constable to the presence of drugs in an seemingly "empty" backpack.
Authorities allegedly found four packages of heroin hidden inside.
Both the driver and the passenger were arrested on a first-degree felony possession of a controlled substance charge.
Investigators said one of the two men is an illegal immigrant.
The two men are expected to be arraigned late Wednesday morning.