An Ohio fertility clinic says an alarm system was turned off on a storage tank that malfunctioned in early March and ruined more than 4,000 eggs and embryos.

A letter sent to patients and obtained by The Associated Press on Tuesday says University Hospitals in suburban Cleveland doesn’t know who shut off the alarm or why it happened.

The hospital says the alarm should have alerted staff to changes in the storage tank’s temperature on March 4.

The letter also says the number of eggs and embryos in the failed tank was double than what it first thought. The hospital says it’s unlikely any of the 4,000 eggs and embryos are viable.

A message seeking comment was left with the hospital.

Several lawsuits have been filed against University Hospitals.