Several large landlords allegedly colluded in an effort to keep apartment rents high, including by using an algorithm that influences prices, according to new legal filings by the Colorado attorney general,

Prosecutors said the landlords used an algorithm to help set rents and privately shared sensitive information with their own competitors to boost profits.

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.

The complaint alleged the six companies set their rents using each other's information by either speaking with competitor's senior managers, calling around, and participating in user groups to discuss how to modify pricing methods.

The U.S. Department of Justice and 10 state attorneys general have ramped up their antitrust lawsuit against RealPage, a property management software compa