The federal corruption and extortion case against Fall River Mayor Jasiel Correia is moving forward at the John Joseph Moakley federal courthouse in Boston as two of his four alleged co-conspirators are expected to enter plea agreements Tuesday.

Officials from Massachusetts' U.S. Attorney’s Office told WGBH News on Monday that Antonio Costa, 51, of Fall River and David Hebert, 54, of Westport are expected to waive indictment and plead guilty to charges of extortion, conspiracy and making false statements to federal officers.

On Sept. 6, federal agents arrested and charged Correia for allegedly extorting marijuana vendors for hundreds of thousands of dollars in bribes in exchange for non-opposition letters to operate their marijuana businesses in Fall River.

Correia is also charged with extorting a building owner for cash and a Rolex watch in exchange for activating the water supply to a commercial building and demanding his chief of staff give him half of her salary for appointing her and allowing her to keep her city job. Correia is free on $250,000 secured bond but is restricted to remaining in Massachusetts and Rhode Island.

Costa and Hebert are accused of participating in the extortion scheme and lying to federal investigators.

Another co-defendant, Correia's former chief of staff and campaign manager, Genoveva Andrade, faces extortion, conspiracy, and bribery charges. On Monday, Andrade’s probable cause hearing was delayed as her defense attorney, Charles Rankin, sought to question federal agents involved in the case.

A fourth alleged co-conspirator, Hildegar Camara, 58, of Fall River is due in federal court on Thursday.

The Fall River City Council last week voted to temporarily oust Correia as mayor, but Correia maintains his innocence and has refused repeated calls to step down as mayor. The council may go to court on Wednesday to seek to permanently remove him. He faces a preliminary mayoral election on Tuesday.