Insurance brokerage Willis Group Holdings has been accused of contributing to the massive fraud allegedly perpetrated by Allen Stanford and his Houston-based firm, Stanford Financial Group.

A group of former Stanford depositors from Mexico say they were defrauded by Willis and codefendants Bowen, Miclette & Britt of Houston, and two individuals, according to a statement from the law firm representing the investors, Strasburger & Price. The class-action suit was filed in federal court in Texas.

The suit accuses Willis and codefendants of supplying Stanford Financial with “safe and soundness” letters, which the group used to retain or obtain actual or prospective clients, according to the law firm. The depositors also allege that the accused financial groups acted as sales agents for Stanford Financial, who convinced Latin American depositors to invest with and then be defrauded by the financial services firm, resulting in a several billion-dollar loss.

“This marks an important first step to recover financial assets for defrauded clients beyond what the United States government is currently pursuing,” said Edward F. Valdespino, co-lead lawyer of the Latin American depositor clients, in a statement. “For depositors who literally risk losing everything, the U.S. Federal Court offers a real chance to seek financial recourse for their losses.”

In a separate criminal case, federal authorities accuse Stanford and his firm of a $7 billion scheme to defraud investors, for which he is awaiting trial, scheduled in August. Stanford was charged in a 21-count federal indictment with bilking hundreds of investors. He could face life in prison, if convicted of all charges.