A self-proclaimed electronics surveillance expert was accused Saturday of turning over blank tapes to federal authorities after claiming they would reveal the Tawana Brawley rape case as a hoax.

Samuel McClease, 26, was ordered held without bail after federal officials charged him with one count each of obstruction of justice and perjury.McClease had publicly claimed Monday that the Rev. Al Sharpton, one of the advisers of the black 16-year-old Wappingers Falls girl who said she was raped by six white men last November, had hired him to bug conversations involving her two lawyers, activists C. Vernon Mason and Alton Maddox Jr.

McClease said two of the eight hours he taped showed that the three men, who have advised the girl not to cooperate with a grand jury or investigators, knew Brawley's story was groundless.

Although hospital tests found no sign of rape after Brawley was found last November in a plastic bag, smeared with dog excrement and racial epithets, the case has become a civil rights cause. Mason, Maddox and Sharpton say Brawley is the victim of a racist cover-up.

"This is, of course, another unexplained development in a case that has been full of many surprising twists and turns," said Scott Greathead, first assistant state attorney general, at a news conference following McClease's detention hearing.

U.S. Magistrate Kathleen Roberts continued the hearing until Monday afternoon after Assistant U.S. Attorney Federico Virella asked for time to gather witnesses.

Virella charged that McClease, 26, of Jersey City, N.J., had "played games with the government" and was a "very, very serious risk to flee."

In a complaint signed by FBI special agent Judith K. Lewis, the government charged that McClease turned over two reels of reel-to-reel tape and eight cassette tapes, all of which were blank. The two reels appeared never to have been used, Lewis said.

On Saturday, Sharpton said he wasn't surprised that the tapes were blank.

"I think what this does is confirm what we've been saying all along," Sharpton said. "There's a concerted effort to discredit black leadership in general, me in particular, for the last few months. This man being exposed as a liar shows that."

According to the government complaint, McClease first appeared before the federal grand jury on Wednesday and refused to produce the tape recordings. U.S. District Court Judge Shirley Wohl Kram then ordered him to do so, and gave him a highly limited form of immunity solely for the act of producing the tapes for the grand jury.

The complaint said McClease, a former Navy technician, appeared again on Thursday and turned over what he said were original tapes of conversations among the Brawley advisers.

The tapes were turned over to the FBI for duplication, the complaint said. "During the course of duplication, FBI audio technicians determined by observing the audio level that all of the original tapes produced by McClease were blank and that in their opinion the two reels looked fresh and never . . . used."

Mason and Sharpton have disavowed knowing McClease and suggested he is a government agent.

Sharpton is under investigation by the Internal Revenue Service for failure to file income taxes and reportedly by a state grand jury for alleged personal use of charitable donations.