The Aryan Strikeforce was active in Phillipsburg in 2016, according to the Southern Poverty Law Center.
The FBI's early-morning raid on a Phillipsburg home targeted white supremacists, sources said.
About 50 federal agents surrounded the home at 487 S. Main St. at 5:45 a.m., blocking off a section of the street.
The agency has not yet released an official statement or announced any charges. Sources with knowledge of the investigation said white supremacy was a focus but they weren't authorized to speak about it.
The Aryan Strikeforce was active last year in town, according to the Southern Poverty Law Center, which in February released its annual list of hate groups nationwide.
Report: 3 hate groups active in Lehigh Valley
"It's more than just a guy in his basement. That's for sure," SPLC senior investigative reporter Ryan Lenz told lehighvalleylive.com.
Neighbors on Thursday also told reporters of suspected white-supremacist activity.
During the raid, one resident, who declined to be identified, said that people at that address wore black clothes and boots and made hand signals to each other. One allegedly had a "white power" tattoo on his head. The neighbor said he had lived there 28 years, and that the residents at 487 have been there six months to a year.
Later Thursday morning, Chris DeLorenzo, who lives a few doors down, said that he had seen vehicles with Nazi symbols pull up there before.
A woman outside 487 S. Main St. a couple of hours after the raid declined to talk to a reporter. She walked inside and closed the door.
Steve Novak may be reached at snovak@lehighvalleylive.com. Follow him on Twitter @type2supernovak and Facebook. Find lehighvalleylive.com on Facebook.