A third man connected to former D.C. Council member Harry Thomas Jr.’s embezzlement of more than $300,000 in city funds will soon plead guilty, the man’s attorney said Friday.

The news came as Marshall D. Banks, 71, pleaded guilty in the District’s federal court Friday to concealing and failing to report Thomas’s theft. Vandy Jamison, who represents Banks, said that James Garvin — an associate of Banks’s who is also Jamison’s client — plans to submit a similar plea next week. Jamison declined to comment further.

Banks agreed to cooperate with prosecutors as part of his plea agreement.

Thomas, a Democrat, resigned from his Ward 5 seat Jan. 5, a day before pleading guilty to charges of theft and embezzlement of $353,000 in D.C. funds between April 2007 and August 2009. Prosecutors said that Thomas used the money to fund a posh lifestyle that included pricey cars and trips. He faces a possible term of 37 to 46 months in prison when he is sentenced in May.

According to Banks’s plea, his youth sports organization Lang­ston 21st Century Foundation received $392,000 in 2008 from the Children & Youth Investment Trust Corp., a public-private nonprofit group established by former Mayor Anthony A. Williams. At Thomas’s instruction, Banks cut $306,000 in checks to two Thomas entities, ostensibly for grant-related activities.

But before October 2008, Banks was aware that reports prepared by Thomas’s team about the use of those funds were inaccurate, according to court documents.

Garvin, a golf pro at the John Mercer Langston Golf Course in Northeast Washington, worked with Banks as the Langston Foundation’s program director. Banks and Garvin “participated in the grant process and thereby concealed Thomas’s misappropriation of funds,” court papers say.

It is not clear whether more people will be charged in connection with Thomas’s embezzlement. Prosecutors would not comment Friday.

Banks and Garvin were first linked to the case in June, when D.C. Attorney General Irvin B. Nathan filed a lawsuit against the Langston Foundation and its principals. A settlement was reached for $86,000; Thomas agreed to repay the majority of the funds in his own settlement.

U.S. District Judge John D. Bates made clear Friday that Banks’s plea agreement is contingent upon Garvin’s plea. Banks pleaded guilty to misprision of a felony, a felony that carries a maximum three-year prison sentence.

Jamison said that Banks would retain his post as a professor of kinesiology at Howard University, which supplies many of Langston 21st’s volunteers, and continue his work with the nonprofit organization. A Howard spokeswoman declined to comment.