Loudoun County Sheriff Donald L. Lacy is being investigated by Virginia officials on allegations of official misconduct and possible criminal activity.

Circuit Court Judge Carlton Penn, in an order unsealed yesterday, selected Richmond Commonwealth's Attorney Aubrey Davis as a special prosecutor and directed him to investigate "allegations of misfeasance, nonfeasance, malfeasance or criminal activity" involving Lacy, a 34-year-old Republican.

Davis yesterday declined to discuss the details of allegations, which were not disclosed in the judge's order. A county official, who asked not to be named, said the numerous allegations involve misuse of sheriff's employes; that Lacy often fails to show up for work, and other accusations.

"In light of the allegations and out of fairness to the sheriff and the public they ought to be fully investigated and cleared up," Davis said in an interview yesterday.

Lacy, who ousted Loudoun's longtime sheriff Robert Legard two years ago in a major upset, could not be reached for comment.

Special prosecutor Davis said he had not talked to Lacy, but had spent the day in Leesburg meeting with several people he would not identify and with Loudoun's chief prosecutor Thomas Horne.

Horne last week wrote a letter to Judge Penn, detailing the allegations against the sheriff and asking him to name a special prosecutor to investigate them. The judge sealed the letter and immediately asked Davis, a Richmond Democrat, to begin the investigation.

Horne said yesterday he disqualified himself because, as Loudoun's chief prosecutor, he has daily dealings with Lacy, Loudoun's top police officer, and the sheriff's department.

Some of the "numerous allegations" against Lacy were "just outrageous," Horne said. Others were more serious and merited a formal investigation, he said. "You just can't let this kind of thing smolder," Horne said.

Davis said he planned to return to Richmond last night and to "make a decision about how to proceed." There is no time limit on his probe, he said.

Lacy's defeat of Legard, who had been sheriff of the county for 16 years, was seen as a measure of the growing influence of the rapidly developing eastern half of Loudoun. Lacy, who was one of Legard's former deputies, won the election charging that his former boss was a "country sheriff" who was insensitive to the increasingly suburban county.