A federal judge declared a mistrial yesterday in the conspiracy and bribery case against D.C. contractor John B. Clyburn and former federal housing official James E. Baugh after the jury reversed a vote to convict Clyburn on two charges.

It was the second time in three months that a mistrial was declared in the case against Clyburn and Baugh, who are accused of attempting to manipulate a $400,000 federal housing contract for personal advantage.

Two jurors said the reversal occurred when a juror announced yesterday that she had changed her mind during the weekend for reasons they said she did not articulate.

According to U.S. Attorney Jay B. Stephens and the two jurors, the unusual chain of events began Friday when the jurors told U.S. District Judge Joyce Hens Green they had reached a unanimous verdict on two counts against Clyburn, one for conspiracy and one for bribery.

They were unable, however, to reach a verdict on the remaining counts against Clyburn and Baugh, a former high-ranking official at the U.S. Department of Housing and Urban Development.

The judge did not ask the jurors to announce the partial verdict because Clyburn's attorney, Thomas Dyson, said his client preferred that they complete their deliberations.

Green then dismissed the panel for the weekend, instructing jurors to return Monday to deliberate further on the other counts. The jury was not sequestered.

In a note at 10:10 a.m. yesterday, jury foreman Stanley R. Bliss told Green that "upon further deliberations, the unanimous decisions for Mr. Clyburn on Count 1 and Count 2 have been changed to undecided and the jury is now hopelessly deadlocked."

After declaring a mistrial, the judge allowed prosecutors and defense attorneys to interview the jurors. According to sources, at least one juror told prosecutors that the juror who changed her mind seemed to believe that Clyburn was being unfairly prosecuted because he is black.

However, the two jurors contacted said they did not hear the woman express a racial reason for her switch. The jury consisted of nine black women and three white men.

One of the jurors said there was no racial discussion during deliberations. She added that although the jurors believed the government had a good case, they did not attempt to argue with the juror who changed her mind.

Stephens said yesterday that he would review the case to determine whether to retry it.

In addition to being the second mistrial involving Clyburn and Baugh, the judge's action yesterday marked the fourth time in less than a year that the government has been unsuccessful in a public corruption case involving Clyburn. He is a onetime close associate of former D.C. mayor Marion Barry's and did extensive business with the District and federal governments.

Clyburn was acquitted in July, along with former D.C. Department of Human Services head David E. Rivers, of charges that they conspired to steer $2 million in city contracts to companies owned by Clyburn or his friends.

In the fourth trial, two other health officials from the Barry administration, Gladys Baxley and Michael Davis, were acquitted in December of charges that they conspired to defraud the District by manipulating contracting procedures. In addition, the jury was unable to reach a decision on a single count of conspiracy against Davis, who was a close friend of Clyburn's.

The cases, which were the product of a probe begun in 1986 that focused on allegations of contracting improprieties in the Barry administration, involved more than nine months of FBI wiretaps of Clyburn's offices.

In the case that was declared a mistrial yesterday, Clyburn was accused of conspiring with Baugh to win a $400,000 HUD contract in exchange for giving Baugh's wife, Veatrice, business help. That aid allegedly included a part-time job at a Clyburn-owned business and help in securing a $45,000 contract with the D.C. Department of Employment Services.

According to Stephens, an "overwhelming majority of jurors voted to convict" Baugh. One juror confirmed yesterday that the jury split generally 9 to 3 to convict Baugh.

Stephens said the jury's "action will not dissuade this office from seeking to hold accountable those who violate the public trust."

Baugh declined to comment. Clyburn said, "The saga goes on."