PORTLAND, Maine (AP) — Maine’s largest hospital has notified the Maine Center for Disease Control of a patient who has what they believe is a potentially deadly prion disease.

The Maine CDC tells WMTW-TV they were notified by the hospital on Tuesday evening. Testing is underway to reach an official diagnosis.

Prion diseases are rare progressive neurodegenerative disorders. They are believed to be caused by prions, which are infectious agents made of protein. The diseases are fatal in most cases.

Maine Medical Center says in a letter to doctors obtained by WMTW-TV that it was postponing operating room procedures on Wednesday.

The hospital has postponed elective surgical procedures at its Bramhall campus that were scheduled for Wednesday and Thursday and is sterilizing equipment and surgical areas.