IRS Criminal Investigation Agents. They are at any of the big drug or corruption busts. The IRS is the only government agency that can seize property without due process. This is how the cars, boats, houses, airplanes and all the other stuff gets seized instantly.
They say the same thing about the Coast Guard, fish cops (who may be state or fed but I'm talking fed on saltwater), game wardens, and a zillion other government agencies.
I think really any of them can, ie get arrested driving your vehicle all they gotta do is say they may need it for an investigation and even if someone is there to drive it they can impound it.
And unless there's a law backing you actually forfeiting the property, based on you breaking some law, they are gonna have to give your shit back too. IRS can probably show up and confiscate your couch during a routine audit legally, but if they can't link it to criminal profits then it's coming back.