(NewsNation) — The Department of Justice filed an antitrust lawsuit accusing six of the nation’s largest landlords of participating in algorithmic pricing schemes that harmed millions of renters in more than 40 states. 

In an amended complaint filed Tuesday, the Justice Department added six massive landlords to an existing antitrust lawsuit against real estate software company RealPage Inc.

These include Greystar Real Estate Partners LLC; Blackstone’s LivCor LLC; Camden Property Trust; Cushman & Wakefield Inc and Pinnacle Property Management Services LLC; Willow Bridge Property Company LLC and Cortland Management LLC.  

Together, these six landlords operate more than 1.3 million units in 43 states and the District of Columbia. 

The agency alleges these six participated in an unlawful scheme to decrease competition among landlords in apartment pricing by using each other’s competitively sensitive information through common pricing algorithms. 

The amended complaint tacks onto an earlier lawsuit against real estate software company RealPage Inc., which alleged the company violated antitrust laws through its algorithm that landlords use to get recommended rental prices for millions of apartments across the country.

The amended complaint added attorneys general of Illinois and Massachusetts as co-plaintiffs, increasing the total number of state and commonwealth coplaintiffs to 10. Attorneys general of California, Colorado, Connecticut, Minnesota, North Carolina, Oregon, Tennessee and Washington have already joined the suit.

“While Americans across the country struggled to afford housing, the landlords named in today’s lawsuit shared sensitive information about rental prices and used algorithms to coordinate to keep the price of rent high,” acting Assistant Attorney General Doha Mekki of the Justice Department’s Antitrust Division said in a statement.

“Today’s action against RealPage and six major landlords seeks to end their practice of putting profits over people and make housing more affordable for millions of people across the country.”

Rents across the U.S. saw a huge spike in 2021 and 2022, and though their growth has since tapered off, they remain stubbornly high for many tenants, thanks in part to a huge lack of housing supply. Justice Department officials allege that RealPage is another reason for the high rents since the algorithm allows landlords to align their prices and avoid competition that would otherwise keep rents down.

Justice Department officials said these landlords coordinated through a variety of means, including directly communicating with competitors’ senior managers about rents, occupancy and other competitively sensitive topics, sharing information with competitors about parameters in RealPage’s software and discussing via user groups how to modify the software’s pricing methodology as well as their own pricing strategies. 

The Justice Department also announced a proposed consent decree that, if approved by the court, would resolve its claims against Cortland, a landlord that manages over 80,000 rental units in 13 states.

Under the proposed consent decree, Cortland would cooperate in the Justice Department’s investigation and be barred from using competitors’ competitively sensitive data to train or run any pricing model and using third-party software or algorithms to price apartments without the supervision of a court-appointed monitor among other requirements.

The Associated Press contributed to this story.