The biggest U.S. pension fund has sued the top three ratings agencies in a complaint linked to big losses linked to complex investments.

Calpers filed a suit against Moody’s Investors Service, Standard & Poor’s and Fitch, accusing them of misrepresenting a complex form of debt called structured investment vehicles, which can contain a variety of assets.

The suit was filed in California Superior Court in San Francisco late last week, according to the New York Times. Calpers bought $1.3 billion of SIVs in 2006, which collapsed in 2007 and 2008, according to the report.

The suit states, a top level AAA rating from the agencies “proved to be wildly inaccurate and unreasonably high,” according to the suit, the report stated. The fund did not specify an amount of damages it is seeking.