ANNAPOLIS, Md. (AP) — A married pair of top officials in a Maryland county is accused of tampering with evidence after FBI agents said they recorded the husband telling his wife to flush a $100,000 check from a real estate developer down the toilet and to stuff almost $80,000 in cash in her underwear.

Prince George’s County Executive Jack Johnson, whose second term expires next month, and his wife, Leslie, who was recently elected to the County Council, were charged with witness and evidence tampering and destruction, alteration and falsification of records in a federal investigation.

The charges grew out of a 5-year-old investigation into allegations of real estate developers in the county offering rewards to county officials in exchange for personal and business favors.

In an affidavit filed in federal court, FBI agents wrote that they recorded a mobile phone conversation between the Johnsons after agents went knocking on their door.

After Johnson told his wife, “Don’t answer it,” he instructed her over the phone to go upstairs to their bedroom and destroy the check, the affidavit said.

“Tear it up! That is the only thing you have to do,” Johnson told his wife, according to the affidavit.

Leslie Johnson then could be heard asking her husband, “Do you want me to put it down the toilet?”

The county executive responded, “Yes, flush that,” according to the affidavit, which noted that monitoring agents heard a flushing sound in the background.

Johnson then told his wife to put cash in her underwear, according to the affidavit. After FBI agents entered the home, they searched Leslie Johnson and recovered $79,600 from her underwear.

The Johnsons were arrested at home and released later on personal recognizance. Jack Johnson was placed on home detention with electronic monitoring. They both face a maximum of 20 years in prison.

Jack Johnson swore his innocence after being released: “To all the citizens of Prince George’s County, you know me. I‘ve served you long and I’ve served you well and most of you know me well. I cannot go into these allegations because my lawyers will kill me if I do. I’m innocent of these charges. I just can’t wait for the facts to come out. When they come out, I am absolutely convinced that we will be vindicated.”

Roland Patterson, Leslie Johnson’s attorney, said she is asking for prayers and support “through the ordeal of fighting to disprove the allegations that are pending against her now.”

U.S. Attorney Rod Rosenstein said authorities have tapped Jack Johnson’s phone since January 2010. Prosecutors expect more charges to be filed and more people to be charged.

Jack Johnson, 61, has been county executive since 2002; his term ends in three weeks. The Democrat was the county state’s attorney for eight years before that. Born in Charleston, S.C., Johnson attended Benedict College and got his law degree from Howard University, where his wife was also a law student.

Leslie Johnson, 58, worked for the District of Columbia government for nearly three decades before running for a seat on the council. She has been honored for her work in education and for a program she co-founded that provides support for women in jail. The couple has three children.

Prince George’s County borders Washington D.C. and is the wealthiest county in the U.S. with an African-American majority.