Border Patrol agents in the Tucson Sector discovered more than 50 pounds of pills containing suspected fentanyl hidden under the bed of a pickup this week as seizures of the synthetic opioid continue to surge at the southwest border.

Taking just one pill containing the deadly substance can be fatal, and the U.S. Drug Enforcement Agency says 42% of the illicit pills tested for fentanyl contain at least two milligrams of the drug,which is considered to be a lethal dose.

fentanyl

Fentanyl pills   (U.S. Drug Enforcement Adminstration)

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U.S. Customs and Border Protection reported they stopped a white Ford F-150 Monday morning at the Interstate 19 immigration checkpoint near Amado, Arizona, when a canine alerted agents to the truck.

Using the dog's nose and imaging technology, the agents uncovered a compartment hidden under the bed where a trove of 53 pounds of pills was found.

fentanyl border patrol

U.S. Border Patrol agents working the Interstate 19 immigration checkpoint near Amado, Arizona, seized over 50 pounds of suspected fentanyl and arrested the driver of the vehicle on Oct. 11, 2021. (U.S. Customs and Border Protection)

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A press release said that the pills "tested positive for the characteristics of fentanyl."

Agents arrested the 33-year-old driver of the vehicle, described as a female U.S. citizen. She was handed over to the DEA for prosecution.

border patrol

A U.S. Border Patrol agent patrols Sunland Park along the U.S.-Mexico border next to Ciudad Juarez.  (AP Photo/Russell Contrera)

Fentanyl is typically manufactured in Mexico, and cartels send the illicit drug across the border for distribution across the U.S. where opioid deaths have become a crisis.

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Officials have seized roughly 10,000 pounds of fentanyl at the southern border so far in fiscal year 2021, along with 180,000 pounds of meth, 86,000 pounds of cocaine, 5,000 pounds of heroin and 311,000 pounds of marijuana.

Fox News' Ashley Soriano contributed to this report.