A routine inspection at a Philadelphia port last week resulted in the confiscation of $1.7 million worth of the dangerous opioid fentanyl, which had been shipped from China, federal authorities said.

A drug-sniffing dog detected the fentanyl inside barrels of iron oxide, Philadelphia's FOX 29 reported.

U.S. Customs and Border Protection agents found 50 packages of the “white, powdery substance,” a CBP release said. Officers later positively identified the substance as fentanyl.

The drugs weighed a total of 110 pounds, and had a street value of $34,000 per kilogram, authorities said.

“Opioids, including fentanyl and its analogues, are a serious public health concern, and the importation of vast amounts of this deadly synthetic chemical compound is a national security threat,” the release said, quoting a CBP agent. “Customs and Border Protection remains committed to keeping our communities safe by combatting the flow of illicit drugs, including synthetic opioids, into the United States.”

According to CBP, fentanyl seizures have been on the rise since the agency began recording the seizures in 2016. In that year, officers seized 440 pounds nationally. The number grew to 951 pounds in 2017, 984 pounds by April 2017.

On Tuesday, the Philadelphia Inquirer reported that 20 crack cocaine users had overdosed during the preceding 10 days. Two of those people, the report said, had unknowingly consumed fentanyl.