PHP error: cannot redeclare class - php

Question

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class dept_officer extends CI_Model{
function __construct()
{
parent::__construct();
}
function get_sponsorship_list()
{
$this->db->from('tbl_donor');
$this->db->join('tbl_sponsorship', 'tbl_donor.DonorId = tbl_sponsor.DonorId');
$query = $this->db->get();
return $query->result();
}
function get_programme_list()
{
$this->db->from('tbl_program');
$this->db->join('tbl_sponsorship', 'tbl_program.SponsorshipId = tbl_sponsor.ponsorshipId');
$query = $this->db->get();
return $query->result();
}
function get_child_list()
{
$this->db->from('tbl_child');
$this->db->join('tbl_family', 'tbl_child.FamilyID = tbl_family.FamilyID');
$this->db->join('tbl_school', 'tbl_child.SchoolID = tbl_school.SchoolID');
$query = $this->db->get();
return $query->result();
}
function get_crpo_list()
{
$this->db->from('tbl_crpo');
$this->db->join('tbl_district', 'tbl_ds_division.DistrictI = tbl_district.DistrictId');
$this->db->join('tbl_dsdivision', 'tbl_crpo.ds_divisionId = tbl_ds_division.ds_divisionId');
$query = $this->db->get();
return $query->result();
}
}
?>
I've created this class to contains all the queries to display list of different users in the system. i get a compile error saying cannot redeclare class dept_officer even though i haven't tried to declare any classes.
The above is the code for the model in codeigniter