The city of Fresno has joined two other California municipalities in a federal antitrust suit alleging that some of the country’s largest banks conspired to manipulate aspects of the roughly $2.6 trillion municipal bond market.

Fresno, following similar suits filed earlier this year by Alameda County and the city of Oakland, has accused a number of financial institutions of conspiring to rig the process whereby banks bid to sell to municipalities certain vehicles, called derivatives, for investing their bond money.