Officials at Ste. Justine Hospital have identified the particles found in its drinking water as copper oxyde, a compound found in vitamins, among other things, and have lifted the ban on drinking tap water in most areas.

An employee spotted black particles in the water either on Monday or over the weekend, and ever since the hospital has been trying to figure out where those particles came from.

The concentration of the particles is still high in one area of the hospital so the ban remains in effect there. The hospital ran repeated tests on the water, and pipes and water mains in the area have been examined as well. The results came in late Friday afternoon.

The particles are not toxic, however to be cautious they told staff and patients not to drink water from the fountains or taps at the hospital. The ban lasted five days.

Patient care wasn't affected because sterilized water is used for surgery and for patients will weak immune systems. However, it was an inconvenience as filters had to be used for the kitchens and in some bathrooms.

The hospital hasn't figured out how the particles ended up in the water and is still searching for the source,.