Federal officials made the largest seizure of fentanyl in U.S. history on Saturday. Customs and Border Protection officers said Thursday they discovered 254 pounds of the synthetic opioid, which is responsible for the majority of drug overdose deaths, hidden in a floor compartment of a truck loaded with cucumbers thanks to the sensitive nose of a drug-sniffing dog. Officials also found 395 pounds of methamphetamine. The truck was stopped trying to enter the U.S. through the border checkpoint in Nogales, Arizona. CBP valued the fentanyl at $3.5 million and the methamphetamine at $1.1 million. The seizure is more than twice the size of the previous record of 118 pounds, which was found in a truck stopped by state troopers in Nebraska in 2017. The Centers for Disease Control said fentanyl—which users often incorrectly believe is heroin—was responsible for more than 28,400 overdose deaths in 2017, the latest year for which figures are available. Fentanyl is up to 100 times stronger than morphine, which heroin derives from.