PESQ range from PESQ.p files on ITU website

In most of literature I have read, the range of PESQ values is from 0.5~4.5. But the files I downloaded from ITU website for PESQ calculation is sometimes giving negative answers too. As those Matlab functions are in "Protected Mode", so I could not open them. Kindly if you know what can be the output range of PESQ which can be expected from the files on the ITU website"

Hoping for quick response. Thanks in advance.