Families are being contacted by the hospital, asked to come in for blood tests for HIV and Hepatitis. The hospital spokeswoman describes the risk of HIV or Hepatitis B or C as “extremely low.”

It is unclear how long the problem has been going on.

Seattle Children’s is notifying families of all 12,000 patients treated at the Bellevue surgery center over its-five year history.

The cause of the problem is under investigation, and the equipment in question has been taken out of service. The spokeswoman did not elaborate on what the specific equipment was.