The FBI has closed an investigation into allegations that bodies of black people killed by the Ku Klux Klan were buried in a mass grave in Fauquier County after the Nevada inmate who made the claims failed a polygraph test this week, authorities said yesterday.

The agency began the investigation in February after Edward Allen See, 43, who is serving two consecutive life sentences at Ely State Prison in Nevada, told them that 50 black people who had been killed by the Klan were buried in the county.

See, who failed part of a polygraph administered by the FBI in March, was given a second test at Ely Tuesday. Based on information in that test, the investigation was dropped, said FBI public affairs chief Thomas F. Jones.

"Based on information we received today, we have discounted the information provided by Mr. See to date and no further investigation will be done," Jones said. "A second polygraph was given and an evaluation and review of that led us to believe that no further reaction is required in this matter."

William F. Dwyer, a Beverly Hills lawyer who represents See, said he was disappointed with the FBI's decision. He urged the FBI to verify or discredit See's claims by conducting an excavation of the alleged grave site.

"If the FBI has chosen to close the investigation based on Eddie See's polygraph examination, then it appears sweat {affecting the polygraph} is considered more reliable than a backhoe in unearthing what may or may not be buried remains of Klan killings," Dwyer said. He said See wanted an independent polygraph test.

See said that he "participated" in the killings of several blacks kidnapped from the Washington area and was a member of the Klan from 1961 until 1964.