LAFAYETTE — Fifteenth Judicial District Attorney Mike Harson said Tuesday he does not believe anyone else in his office was knowingly involved in the bribery scheme that his former secretary and office administrator admitted to on Monday.

Barna D. Haynes, 58, of Lafayette, pleaded guilty to one count of conspiracy in an ongoing federal investigation of bribes that were paid for giving criminal defendants a break, mainly in DWI cases.

“I’m obviously dismayed over the results,” Harson said. “She was a trusted employee for a number of years. Hopefully, that chapter is over. … This all came as a big surprise to a lot of people who knew Mrs. Haynes.”

U.S. Attorney Stephanie Finley has said she anticipates more guilty pleas in the investigation.

Harson said Tuesday he could not speculate on who might be charged but no one else in his office has resigned, been terminated or placed on leave in connection with the case.

Prosecutors allege a person identified in court documents only as “co-conspirator No. 1” paid Haynes $500 per case.

In return, Haynes routed many of the defendants into a special program in which the charges were quickly dismissed if they successfully completed certain probation requirements, such as drivers safety classes, substance abuse treatment and community service, prosecutors said.

Haynes admitted to accepting $55,000 in bribes, but prosecutors contend the amount exceeded $70,000.

Prosecutors wrote in court filings that the bribery scheme went on for about four years without Harson’s knowledge, in part because of a “lack of oversight and safeguards.”

All of the deals arranged by Haynes were approved by a judge in special court sessions handled by the same assistant district attorney in Harson’s office, federal prosecutors have said.

Prosecutors did not identify that staff member.

Harson said he does not believe the staff member who handled the deals knew they were arranged pursuant to a bribe.

“His role was simply carrying out instructions,” Harson said.

Prosecutors allege the bribery lasted from March 2008 though 2012.

Haynes, who resigned in August, was placed on leave about two weeks after the FBI searched the District Attorney’s Office on Feb. 27, 2012.

She faces up to five years in prison and has agreed to cooperate with federal investigators.

Finleydeclined Monday to comment on how many other people have been targeted in the case.

The state Attorney General’s Office has a related investigation into possibly falsified verifications of community service hours that were submitted as part of the same types of special plea agreements that are the subject of the federal investigation.

The special plea deals usually required proof that community service hours had been completed.

State Attorney General’s Office spokeswoman Laura Gerdes Colligan confirmed via email on Tuesday that the investigation is pending but declined to offer any further details.

Harson had asked the state attorney general to look into the issue.

He said Tuesday that his office has implemented more-stringent requirements for the verification of community service hours.