Someone apparently sabotaged several of the O-rings produced for space-shuttle boosters, but officials say they are confident that none of the damaged rings were shipped to the factory that builds the rockets.

FBI and National Aeronautics and Space Administration investigators are probing the case of razor-slashed silicon O-rings first discovered last June, company officials said Thursday.HydraPak Inc., of West Jordan, "discovered during normal procedures in the manufacturing process certain space-shuttle O-rings appeared to have received damage of a suspicious origin," said James Dockstader, company vice president for operations.

Faulty O-rings were blamed for the shuttle Challenger explosion Jan. 28, 1986, according to the presidential commission that investigated the disaster. All seven crew members were killed.

But Dockstader said that "no damaged O-rings were shipped to Morton Thiokol" Inc., the manufacturer of the booster rockets for the space shuttle.

HydraPak, the sole supplier of O-rings for the shuttle, contacted "appropriate individuals at Morton Thiokol" immediately after discovering the apparent sabotage, he said.