Officials in Medicine Hat say they may never know where an infestation of rats originated.

City workers may have bested the rats, but manager of solid waste, Ed Jollymore, says they’re still unsure of how they got there in the first place.

Jollymore tells The Calgary Herald there are several different places that bring waste into their landfill.

The province’s rat patrols were victorious last month when they eradicated a massive 80 metre nest in the dumping ground.

Close to 150 rats were killed in the city and surrounding areas.