The AFTRA Retirement Fund has filed a federal lawsuit against JPMorgan Chase Bank over losses in millions of dollars that the plan sustained through the Sigma Finance hedge fund.

The pension fund filed the suit, which seeks class-action status, in U.S. District Court in New York on Jan. 23.

The action alleges that JPMorgan Chase lost a “substantial portion” in cash collateral in medium-term notes issued by Sigma Finance Inc., a structured investment vehicle sponsored by Sigma Finance Corp. It said creditors seized over $25 billion of Sigma’s $27 billion in assets in September and October, leaving about $1.9 billion as security for about $6.2 billion of outstanding medium-term notes.

Pension fund lawyer Darren Check, a partner with Barroway Topaz Kessler Meltzer & Check, told Daily Variety, “We feel that the fund has been wronged by the bank.

The pension fund, which has assets of $1.5 billion, covers members of the American Federation of Television & Radio Artists.

JPMorgan Chase did not respond to a request for comment.