Holtgreve claims she and Dobbs had sex several times at the Rialto Police Benefit Association's union building, and that other officers have keys and routinely meet there for sex.
A police department spokesman says the department's investigation of the charges led to six officers who might have been involved in misconduct, but only the four have been placed on paid leave.
The department has not released the names of the other officers placed on leave.
The Associated Press contributed to this report.
