Updated

A former Georgia prison guard has pleaded guilty in federal court to sexually assaulting three female inmates and then coercing them into helping him cover up the assaults.

Edgar Daniel Johnson, 51, pleaded guilty Monday, admitting that between Nov. 1, 2012, and Sept. 30, 2013, he had non-consensual sex multiple times with three female inmates at Emanuel Women's Facility in Swainsboro, where he worked as a guard, federal prosecutors said in a news release Wednesday.

Johnson also admitted calling Southside Fire Department in Chatham County to report a false bomb threat on Elba Island near the Port of Savannah last May, prosecutors said.

He pleaded guilty to three counts of willfully depriving the inmates of their Eighth Amendment rights under color of law, three counts of obstruction for coercing the inmates into covering up the assaults and one count of maliciously conveying false information about explosive materials.

Georgia Department of Corrections investigators began to scrutinize Johnson after receiving complaints from inmates who described specific scenarios with similarities and details no one else would know, investigator Clay Nix told The Associated Press in 2015. He said at the time that his office had identified more than a dozen women who said Johnson had victimized them.

Johnson was fired in April 2015 and was arrested the following month on multiple state-level charges related to the investigation. His attorney, Kendall Gross, has said Johnson vehemently denied the allegations.

Gross was unavailable Wednesday, but a woman who answered the phone at his office confirmed that he still represents Johnson and that the state charges are still pending.

Four former inmates who said they were victimized by Johnson spoke to the AP in 2015. They said Johnson initially seemed like someone who cared, a comforting presence in a scary place. He said he was a pastor and recited passages from the Bible.

But he quickly began making sexual comments and touching them, they said. He identified their vulnerabilities and used them to manipulate the women into doing what he wanted, the women said.

The AP generally does not name alleged victims of sexual crimes. The three women mentioned in the federal court filings are identified only by their initials.

Three of the women filed a federal lawsuit against Johnson and corrections officials in December 2015. It's not clear whether they are the same women mentioned in the federal charges. A judge in January dismissed the women's claims against the corrections officials, and the case against Johnson is on hold pending the outcome of a bankruptcy filing, according to court records.