Porter Adventist Hospital is canceling most surgeries Friday, a day after it warned people of a breach in the sterilization process of medical instruments used for certain surgeries over the past two years.

The announcement comes after hospital officials noticed “a potential change in our water quality relative to our surgical equipment,” according to a statement from Porter Adventist Hospital spokeswoman Chrissy Nicholson.

The revelation prompted Colorado Department of Public Health and Environment officials to conduct an additional on-site survey Thursday afternoon, noting that while they had “not identified any infections caused as a result of this breach,” they were still investigating “whether additional patients may be at risk,” Dr. Larry Wolk, the CDPHE executive director and chief medical officer, said in a statement.

“The risk of harm from this incident continues to be unknown, but it is thought to be low,” he said.

Because the investigation is ongoing, he said, the hospital voluntarily canceled most surgeries scheduled for Thursday and Friday.

On Wednesday, hospital officials said they were notifying people who had orthopedic or spinal surgeries between July 21, 2016, and Feb. 20 of this year about the breach, which the hospital said could have put some patients at risk of hepatitis B or C, or HIV.

Wolk said the hospital on Wednesday mailed letters to patients who had surgery during the affected period and has established a hotline for patient questions. The phone number to call is 303-778-5694.

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