The Justice Department has expanded a lawsuit against the real estate software company RealPage, adding six of the biggest landlords and property management companies in the country to the suit and alleging that they coordinated to keep rents artificially high.

Millions of rents across the country may now be set using one company’s algorithmic software, according to a federal lawsuit and a Washington Post analysis.

An amended complaint names six landlords as defendants in ongoing litigation that North Carolina and several other states, along with the federal government, began in August.

Creation of a pricing algorithm in coordination with a software company has created a lawsuit by the North Carolina’s attorney general, the federal government and nine

High rent prices in D.C. have long frustrated residents in the District. “When I was looking at prices, I said, ‘Can you write down the prices of the units we saw?’ And they said no because the prices change every day,