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.