U.S. Customs and Border Protection officers assigned to contraband enforcement at the ports of Los Angeles and Long Beach seized 424 pounds of cocaine that had been stashed inside a shipment of tires, the agency reported.

The cocaine, which had an estimated street value in excess of $8 million, was discovered Saturday at the Port of Long Beach when officers using scanning technology saw what the agency called an anomaly within a container carrying tires. Upon inspecting the containers, Customs officers found three large bundles that contained 170 brick-sized packages of cocaine.

No arrests were announced, however Customs officials do not consider the company shipping the tires to be the culprit. Investigators believe the container was tampered with at some point during its transport from South America to the United States by a criminal who hid the drugs inside.

“Without any doubt, this is one of the most significant narcotics interception in recent years at our nation’s largest seaport,” said Carlos Martel, Customs Port Director for the ports of Los Angeles and Long Beach said in a statement.

A photograph supplied by Customs showed officers employed a Rapiscan Eagle M60 unit to find the cocaine. The Eagle M60 is a mobile X-ray scanner built on top of a truck chassis. Rapiscan is a subsidiary of Torrance-based OSI Systems.

Customs spokesman Jaime Ruiz said the agency has deployed X-ray and gamma ray scanning technology to inspect shipping containers for several years. He said the agency adopted the technology after the Sept. 11, 2001 terrorist attacks heightened officials’ concerns that weapons of mass destruction could be smuggled into one of the nation’s ports.

“The technology that is in place for detecting terrorist threats also helps us to find contraband like drugs,” he said.

Nonetheless, Ruiz said it’s rare for Customs officers to find such a large quantity of cocaine on a ship given the highly-regulated nature of the maritime industry.

Customs officers nationwide seized more than 3.8 billion pounds of drugs during the fiscal year that ended Sept. 30, 2014, according to the agency.