SALEM, Mass. (AP) — Hundreds of patients at the Salem Hospital in Massachusetts may have been exposed to hepatitis and HIV over a two-year period, the hospital said.

About 450 endoscopy patients may have been exposed to HIV, Hepatitis B and Hepatitis C during the administration of intravenous medications “in a manner not consistent with our best practice,” the hospital said Wednesday in a statement through its parent company, Mass General Brigham. The hospital learned of the issue earlier this year.

“Once identified, the practice was immediately corrected, and the hospital’s quality and infection control teams were notified,” it said, though it didn’t provide specifics about how the problem occurred.

The infection risk to patients “is extremely low” and there is no evidence so far that any patients were infected, the hospital said.

All patients who may have been exposed have been notified, and the hospital has set up a free hotline to answer questions and is providing free screenings, the hospital said.

During an endoscopy, a tube-like instrument is inserted into the body to look inside, according to the American Cancer Society. Some of the most common procedures are colonoscopies, bronchoscopies, laryngoscopies and upper endoscopies.