AUSTIN, Texas (AP) — Federal investigators have secured a third guilty plea in connection with an investigation into U.S. Rep. Henry Cuellar of Texas on charges that he accepted nearly $600,000 in bribes from an Azerbaijan-controlled energy company and a bank in Mexico.

Irada Akhoundova, 67, pleaded guilty May 1 in Houston federal court to acting as an agent for Azerbaijan without registering with federal officials. Details of her guilty plea were unsealed on May 9.

Federal authorities have charged Cuellar, 68, and his wife Imelda Cuellar, 67, of accepting the money from 2014 to 2021 in exchange for the congressman advancing the interests of the former Soviet republic and the Mexican bank in the U.S. He says they are innocent.

One of Cuellar’s top former aides, Colin Strother, and a Texas political and business consultant, Florencia Roden, struck plea deals in March on felony money laundering charges related to the Mexican bank.

Court records noted Akhoundova’s plea agreement comes from the same investigation, and like the other two, includes that she “fully cooperate with the United States.” The alleged bribes from Azerbaijani interests totaled more than $300,000.

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“As long as Akhoundova tells the truth, then we have nothing to worry about,” Cuellar attorney Chris Flood said Monday. “Congressman Cuellar never agreed to act as a foreign agent and has always voted his conscience and for the best interests of his constituents, consistent with many of his colleagues.”

Akhoundova’s plea agreement described her as an “active member of the Texas Azerbaijani-American community.” It said she worked from 2014-2017 as director of a Texas affiliate of an Azerbaijan energy company, where she transmitted false consulting invoices and helped facilitate payments she thought were “in the interests” of the oil company and the Azerbaijan government.

The agreement also said she knowingly helped set up another Texas affiliate company that would act on behalf of the Azerbaijan government and a state-owned oil company, without registering as an agent of a foreign principal.

Akhoundova faces up to five years in prison. An attorney for Akhoundova has not responded to a message requesting comment Monday.

According to the indictments against the Cuellars, the Azerbaijan energy company initially made the payments through a Texas-based shell company owned by Imelda Cuellar and two of the couple’s children. That company received payments of $25,000 per month under a “sham contract,” purportedly in exchange for unspecified strategic consulting and advising services.

Azerbaijan officials wanted to build support for the country in its conflict with Armenia over disputed territory, the immigration status of Azerbaijani citizens, and promotion of the country as a strategic U.S. ally, according to the indictment.

Among other things, Cuellar agreed to influence legislation favorable to Azerbaijan and deliver a pro-Azerbaijan speech on the floor of the U.S. House, the indictment states.

Cuellar was at one time the co-chair of the Congressional Azerbaijan Caucus and the indictment against him says an Azerbaijani diplomat referred to him in text messages as “el Jefe” or “the boss.”

In addition to bribery and conspiracy, the Cuellars face charges including wire fraud conspiracy, acting as agents of foreign principals, and money laundering. If convicted, they could face decades in prison and forfeiture of any property linked to proceeds from the alleged scheme.