How to export from wpdb to csv without including html tags in table?

Question

I'm having trouble setting up an export from my WordPress install to a CSV file. The data displays fine, but there are 8 rows of HTML displaying above it that I cannot get rid of no matter what I do.

Code as follows:

$filename = 'test-' . time() . '.csv';

$header_row = array(
    0 => 'field1',
    1 => 'field2',
    2 => 'field3',
    3 => 'field4',
);

$data_rows = array();

global $wpdb, $bp;
$users = $wpdb->get_results( "SELECT FIELD1, FIELD2, FIELD3, FIELD4 FROM `TESTTABLE`" );

foreach ( $users as $u ) {
    $row = array();
    $row[0] = $u->FIELD1;
    $row[1] = $u->FIELD2;
    $row[2] = $u->FIELD3;
    $row[3] = $u->FIELD4;

    $data_rows[] = $row;
}

ob_clean();

$fh = @fopen( 'php://output', 'w' );

//fprintf( $fh, chr(0xEF) . chr(0xBB) . chr(0xBF) );

header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0' );
header( 'Content-Description: File Transfer' );
header( 'Content-type: text/csv' );
header( "Content-Disposition: attachment; filename={$filename}" );
header( 'Expires: 0' );
header( 'Pragma: public' );


fputcsv($fh, $header_row );

foreach ( $data_rows as $data_row ) {
    fputcsv( $fh, $data_row );
}

fclose( $fh );

echo "Complete";

die();

?>

Would be much appreciated if I could get a hand with this, as I can't seem to get this data to display without additional stuff up the top!