PHILADELPHIA (WPVI) -- Routine examinations at the Port of Philadelphia led to a big fentanyl bust.U.S. Customs and Border Protection officers seized 110 pounds of the deadly opioid.A narcotics detector dog found the drugs in a shipment of iron oxide that arrived from China on June 25.The seized fentanyl has a street value estimated at $1.7 million.Officials say they used a handheld elemental isotype analysis tool that can identify over 14,000 chemical substances with the use of a laser or infrared beam to determine the substance was fentanyl.CBP said fentanyl seizures are trending up. Officers seized 440 pounds nationally in 2016, and that number grew to 951 pounds in 2017, and it has risen to 984 pounds through April 2018.------