TACOMA, Wash. - Tacoma police say they have made the largest drug bust in the history of the department, taking down a large Puget Sound drug trafficking ring.

Police spokesman Mark Fulghum said an investigation that that included hundreds of hours of surveillance ended with the seizure of 55 pounds of black tar heroin worth more than $2.5 million.

Two Mexican citizens were arrested Friday and are being held pending federal drug and weapons charges.

Fulghum said the drug ring distributed large quantities of heroin throughout the region.

The U.S. Border Patrol and assisted with the investigation and seizure, Fulgham said. The case has been forwarded to the United States Attorney's Office.