Saudi and U.S. officials announced Wednesday that they had ended their search for the remains of Paul M. Johnson Jr., the American military contractor who was kidnapped last month in Riyadh and later beheaded by Islamic radicals.

A group calling itself al Qaeda in the Arabian Peninsula asserted responsibility on June 18 for killing Johnson, an employee of Bethesda-based Lockheed Martin Corp., and posted photos of his decapitated corpse on the Internet. U.S. and Saudi officials said they were certain that the pictures were authentic and that Johnson was dead, but they have been unable to find his remains.

James C. Oberwetter, the U.S. ambassador to Saudi Arabia, said Wednesday that authorities decided to call off the search after running out of clues. "We did everything we could to find Paul and bring him home," he said in a statement released by the U.S. Embassy in Riyadh.

An FBI search-and-rescue team and a squad of hostage negotiators arrived in Riyadh shortly after Johnson was reported missing by his family on June 12. An FBI canine unit that specializes in locating bodies was also deployed to Riyadh after Johnson's death and spent three weeks on the search, U.S. officials said. The FBI and Saudi security forces will continue a criminal investigation in the case, officials said.

Johnson's son, Paul M. Johnson III, had traveled throughout the Middle East in recent weeks in an attempt to publicize the search for his father's body. Embassy officials said that investigators had recovered DNA evidence during the search that is being examined at crime laboratories in Saudi Arabia and Washington but that they did not have any active leads.

Paul M. Johnson Jr., a Lockheed Martin contractor, was kidnapped last month in Saudi Arabia.