Mayor Marion Barry, admitting that "the District government made a mistake," ordered the hiring yesterday of 24 firefighter applicants who were told last month to report to work but then had the offers retracted when it was found that all but one are white.

"It is clear to me . . . that the District government made a mistake, and that our mistake may have caused undue hardship for these 24 persons," Barry said in a prepared statement. The mayor was not available for further comment.

Barry said in the statement he made the decision to hire the 23 men and one woman after receiving a report from Jose Gutierrez, the city's personnel director, and after meeting with Gutierrez, City Administrator Elijah B. Rogers, Fire Chief Norman Richardson and Corporation Counsel Judith Rogers.

Barry said the report concluded that the original job offers to the 24 applicants, issued by telephone on March 15, were "premature" and "an administrative error." The offers were made by a low-level clerk from Gutierrez' office.

The report stated that the offers were "properly withdrawn," but added that the withdrawals created "substantial hardship" for the applicants, five of whom said they quit their jobs to come work for the District. This hardship, the report said, made the status of these 24 applicants a "separate issue" from what Barry insisted all along was the central point of concern -- the fairness of the written examination that produced the list of potential firefighters.

The city reported that a total of 958 persons passed the examination, which was the first such test administered solely by the District government. In years past, the city relied on federal government tests, but for the first time this year was charged with developing its own examination, which cannot by law discriminate against minorities or women.

Of the 958 who passed, 76 percent were black, Gutierrez reported last week. But on a computer-generated list of 100 of those applicants -- from which the 24 were drawn -- 72 were white.

Barry said earlier this week that the 100 names represented "the top" of the list according to test scores, although Gutierrez said a week ago that he did not know how the list of 100 was generated. In any event, both men contended that the city could not hire on the basis of a list that appeared to discriminate.

Meanwhile, officials of the International Association of Firefighters Local 36 began to grumble privately that the union might sue if the 24 whose job offers had been rescinded were not hired. The issue also attracted attention on Capitol Hill, where Rep. Stanford E. Parris (R-Va.), in whose district eight of the affected applicants currently live, charged that rescinding the offers "amounted to breaking a contract" with the applicants.

House District Committee Chairman Ronald V. Dellums (D-Calif.), normally one of the city's strongest supporters in Congress, referred to the incident as an injustice to the 24 applicants. Del. Walter E. Fauntroy (D-D.C.) said he objected to a suggestion by the city that firefighters be hired by lottery.

The city plans to hire 88 new firefighters as soon as possible, starting in groups of 24 -- the largest permissible size for a training class of recruits. But there are currently no plans to hire anyone from the list except the original 24, officials said.

The city announced last week that it will evaluate the examination for possible bias before proceeding with further hiring. That evaluation will proceed, City Administrator Rogers said yesterday, and no hiring will take place until it is completed.

Rogers said the 24 applicants will be informed by telegram on Monday to report to a training class on April 27. A government spokesman said the telegrams will remind the applicants that the city's residency requirement applies to them, and that they must move into the District within six months if they do not already live there.