Montreal's Ste-Justine Hospital has confirmed that four premature babies who died at the hospital in 2004 and 2005 succumbed to infections from bacteria found in plumbing pipes in its neo-natal ward.

Several dozen premature babies have also been sickened from the bacteria, called Pseudomonas aeruginosa.

Dr. Isabelle Amyot, the hospital's medical director, says two other deaths may be related to the bacteria.

The bacterium typically targets the respiratory system, causing pneumonia and septicemia. The premature babies in the neo-natal ward were particularly vulnerable because of their already compromised immune systems.

"A premature baby is extremely fragile to germs that don't affect us,'' Amyot says.

The first death occurred in June, 2004. An investigation into the death lasted several months but failed to find the source of the infection. Three, and perhaps as many as five, other babies died of the same bacterium, but still, the source of their infection was unknown.

CTV Montreal's Annie DeMelt reports that some of the doctors pushed to have the neo-natal ward closed until the source could be found. Hospital officials, with Montreal's Public Health Department's approval, chose to keep the ward in the 50-year-old hospital open.

The unit finally closed in December, 2005, and that's when the bacteria was discovered in the ward's sinks, which were not draining properly.

Amyot says the hospital didn't grasp the scope of the problem at first.

"Every time we thought that the next measure was enough, there were weeks or months without any cases. So we sincerely thought that the problem was over," Amyot explained to CTV Montreal.

Amyot says the hospital has taken many steps since to correct the problem. She says premature babies at the hospital no longer come into contact with tap water; sterilized water is used instead.

There haven't been any related deaths since the changes were brought in.

"I want to be very clear that Ste-Justine is very safe. We have taken all of the measures needed,'' she said.

The hospital is renovating the neo-natal ward. Hospital officials said the new ward is scheduled to open next year.

Sainte-Justine is Quebec's only health care establishment exclusively dedicated to children, adolescents and mothers.