SAN DIEGO — Two civilian defense contractors have pleaded guilty in a San Diego federal court, bringing to nine the number of defendants who have admitted guilt in recent days to their involvement in a scheme involving bribes and kickbacks at Camp Pendleton and other federal facilities.

Federal prosecutors say Paul Dana Kay of PK Excavation and Manuel Ramirez of MRN Construction, Inc., entered the pleas to violations of the Anti-Kickback Act on Friday.