Two Baltimore contractors have pleaded guilty to bid-rigging on a $2.1 million project for the Annapolis Housing Authority.

One of the contractors, Robert K. Kniffin, owner of R & K Contractors, also agreed Friday to cooperate in the ongoing federal probe into charges of fraud and mismanagement at the city agency.

Kniffin and James W. Cox, owner of James W. Cox & Sons, pleaded guilty before U.S. District Judge John Hargrove to one charge of conspiracy to commit fraud involving the Robinwood housing complex.

Under the plea, the result of an agreement worked out with the U.S. attorney's office, Kniffin agreed to cooperate with the investigators in the two-year probe "by describing everything he knows about the awarding of government funded construction contracts" by the housing authority, according to a prepared statement by prosecutors.

Vincent Favazza, a Towson-based contractor who submitted bids on the project but was not indicted, also has agreed to cooperate with federal authorities in the investigation.

Kniffin and Cox, who were scheduled to stand trial Monday in U.S. District Court, face a maximum penalty of five years in jail and a $250,000 fine each. Cox is scheduled to be sentenced Dec. 16, and Kniffin faces sentencing on Jan. 8.