The Justice Dept. and a group of eight states has sued Google (NASDAQ:GOOG) (NASDAQ:GOOGL), accusing the search giant of antitrust violations in its advertising technology business.

Google stock has dipped to tag its session low: (GOOG) -1.5%; (GOOGL) -1.4%.

The plaintiffs are citing violations of the Sherman Act and calling for a breakup of the ad-tech business, which would mark the biggest corporate breakup in decades.

It’s a second major antitrust suit filed by the DOJ, a significant escalation of the department’s anti-monopoly push against the dominant tech giant. Google’s ad business already faced an antitrust suit from a group of attorneys general led by Texas AG Ken Paxton.

The prior suit, filed by the Trump administration and still headed toward trial, charged Google with abusing market power in the Internet search market.

The suit says that Google ran afoul of the law by monopolizing the publisher ad server market illegally; by monopolizing or attempting to the ad exchange market illegally; by monopolizing the advertiser ad network market illegally; and by “unlawful tying” of products to limit competition in publisher ad servers.

Among other remedies it’s looking to “order the divestiture of, at minimum, the Google Ad Manager suite, including both Google’s publisher ad server, DFP, and Google’s ad exchange, AdX, along with any additional structural relief as needed to cure any anticompetitive harm,” as well as enjoining Google from anticompetitive practices.