Local officers, along with ATF, FBI, DPS, ICE and state police showed up Monday morning after spending time in the city on Saturday. Lancaster's police headquarters is being used as a base for the operation.
The U.S. Attorney's office has confirmed that investigators are working on issuing a number of warrants.
ATF officials said it is a federal firearms investigation that could lead to a number of arrests.
Authorities will not release the details of the investigation so as not to tip their hand to any suspect who may face charges.