[oracle] PL/SQL ORA-01422: exact fetch returns more than requested number of rows

I get keep getting this error I can't figure out what is wrong.

DECLARE
*
ERROR at line 1:
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 11

Here is my code.

DECLARE
    rec_ENAME EMPLOYEE.ENAME%TYPE;
    rec_JOB EMPLOYEE.DESIGNATION%TYPE;
    rec_SAL EMPLOYEE.SALARY%TYPE;
    rec_DEP DEPARTMENT.DEPT_NAME%TYPE;
BEGIN       
    SELECT EMPLOYEE.EMPID, EMPLOYEE.ENAME, EMPLOYEE.DESIGNATION, EMPLOYEE.SALARY,  DEPARTMENT.DEPT_NAME 
    INTO rec_EMPID, rec_ENAME, rec_JOB, rec_SAL, rec_DEP 
    FROM EMPLOYEE, DEPARTMENT 
    WHERE EMPLOYEE.SALARY > 3000;

    DBMS_OUTPUT.PUT_LINE ('Employee Nnumber: ' || rec_EMPID);
    DBMS_OUTPUT.PUT_LINE ('---------------------------------------------------');
    DBMS_OUTPUT.PUT_LINE ('Employee Name: ' || rec_ENAME);
    DBMS_OUTPUT.PUT_LINE ('---------------------------------------------------');
    DBMS_OUTPUT.PUT_LINE ('Employee Designation: ' || rec_JOB);
    DBMS_OUTPUT.PUT_LINE ('----------------------------------------------------');
    DBMS_OUTPUT.PUT_LINE ('Employee Salary: ' || rec_SAL);
    DBMS_OUTPUT.PUT_LINE ('----------------------------------------------------');
    DBMS_OUTPUT.PUT_LINE ('Employee Department: ' || rec_DEP);

END;
/

It can also be due to a duplicate entry in any of the tables that are used.