Fairfax County Sheriff M. Wayne Huggins said yesterday more than $10,000 has disappeared from two bank accounts maintained by the county jail and that one senior official has taken an early retirement and another has been demoted because of the incident.

Huggins said at a press conference in the jail that Anthony Benevento, 50, serving time in the jail for forgery, is under investigation by county detectives who are examining the shortage. The sheriff alleged that Benevento stole several checks during the past year, made them out for as much as $6,000 and mailed them to a girlfriend in Prince George's County. She used them to pay off loans on a mobile home and an automobile and to purchase a washer and dryer, not knowing the source of the money, Huggins said.

Benevento had gained the trust of a jail captain and sergeant in charge of the two accounts, Huggins said. He declined to name the officers, saying they were department veterans who had suffered enough embarrassment.

Although checks and bank statements were discovered missing as early as November, Huggins said, the officers failed to notify their superiors of the problem and instead spent months negotiating over the telephone with impostors they believed to be bank officers. The impostors managed to stall the sergeant, delaying discovery of the thefts for several months, Huggins said.

In May the sergeant found one of the missing checks folded in a book on his desk, according to the sheriff. After examining a jail checkbook the sergeant also found two other checks, as well as their stubs, missing.

Neither officer "suspected that anything criminal had taken place," Huggins said. A police investigation of bank records and statements has discovered that six of the missing checks, totaling $10,824, had been cashed by Benevento's girlfriend, the sheriff said.

Huggins said yesterday that the girlfriend did nothing improper and that the two officers were not criminally involved.

Huggins described the captain and sergeant involved as eight- and nine-year department veterans, and said the captain, a 59-year old retired military colonel, had been in a Defense Department job "responsible for handling billions and billions of dollars."

Huggins said that the captain retired last Friday, a few hours before a scheduled disciplinary meeting. The sergeant has been demoted to an entry-level position and salary.