Nine months after Widener Library officials shut off hidden video cameras used in an unsuccessful $50,000 investigation, police have reactivated a number of the cameras in an attempt to prevent thieves from stealing books.

Although numerous police and library officials yesterday denied the cameras in the stacks are in use, a Crimson investigation conducted yesterday found at least one active time lapse video recorder in a basement room in the library.

"I'm the person that's involved with the cameras, but I have no knowledge of what you are referring to," said Sgt. Lawrence J. Fennelly when asked if the cameras has been turned on.

But a display panel on the video recorder--which has a list price of $2,935--read "REC" yesterday and the digital tape counter was active.

A Widener security attendant who spoke on the condition of anonymity said the cameras had been activated within the past two weeks. It is unclear how many cameras are currently linked to the recording device.

Larsen Librarian of Harvard Col- lege Richard De Gennaro refused to confirm ordeny if the cameras had been reactivated, but hedid say there had been a security "incident"recently.

"They aren't destroying books, but, as it is atany other large library, people are ripping usoff," he said.

David Muir, chief of security at Widener, saidhe has no knowedge of the cameras beingreactivated.

Lt. John F. Rooney, who heads the detectivedivision, refused to comment because "it is asecurity matter."

Police Chief Paul E. Johnson, who was inWashington attending the presidentialinauguration, could not be reached for comment.

After an individual known to police as "TheSlasher" mutilated hundreds of books in Widener inthe spring of 1990, police installed between fiveand 10 cameras throughout the library, includingthree hidden in hollowed out books.

Fennelly said that almost all of the camerashad been removed from Widener after thesurveillance project ended in April 1992.Yesterday's Crimson investigation found two of thethree video recorders and a video monitor used inWidener last year, on a desk at the policestation.

But both Fennelly and De Gennaro said not allof the cameras have been taken down. De Gennaroadded that some of the cameras are mobile and canbe placed in trouble spots throughout the library.

The earlier investigation, which cost more than$50,000 failed to produce any suspects, wascriticized for being too expensive and tooobvious.

During the investigation, one officer said thatsome students knew about the cameras and openlyflaunted them.

"I saw a male and a female student discover thecamera and then cover it," said one officer whowatched the tapes. "The camera then went black andI assume they engaged in some sort of sexualactivity."

Police sources said yesterday that they did notknow of anyone's being assigned to monitor thevideotape. De Gennaro said paying officers towatch the tape was unnecessary.

"We are not using people to monitor thecameras," De Gennaro said.

De Gennaro said the current problem is notsimilar to that of "The Slasher," who cut thepages out of Widener books, leaving only thecovers.

"The person is not destroying books," he said."They are using a different modus opperendi."

The recorder observed yesterday was one ofthree AG-6720 Time Lapse Video Camera Recordersowned by the police department. The AG-6720 hasmultiple sensor recording modes and a recordingcapability of more than 480 hours