NEW YORK (AP) — The U.S. Federal Trade Commission is suing Zillow and Redfin, accusing the real estate companies of entering what the regulator says is an illegal deal to suppress competition in online rental advertising.

In a lawsuit filed on Tuesday, the FTC alleges that this agreement started in February — when Zillow paid Redfin $100 million. In exchange for that and other compensation, the commission said, Redfin agreed to end contracts with advertising partners, stop competing ads for multifamily properties for up to nine years and serve as a syndicator of Zillow listings on its own sites.

Redfin also fired hundreds of employees shortly after the announcement of this plan, Tuesday’s complaint notes, alleging that the company also helped Zillow hire “its pick” of these workers.

“Zillow paid millions of dollars to eliminate Redfin as an independent competitor in an already concentrated advertising market — one that’s critical for renters, property managers, and the health of the overall U.S. housing market,” Daniel Guarnera, director of the FTC’s Bureau of Competition, said in a statement Tuesday.