A company that supplied an Ohio fertility clinic's storage tank said its equipment didn't malfunction or cause the loss of more than 4,000 eggs and embryos in early March, blaming the failure on human error.

Custom Biogenic Systems said its initial investigation during the past month concluded that missteps were made at the clinic run by University Hospitals in suburban Cleveland.

The failure and a second one the same day at a fertility clinic in San Francisco were the biggest such losses on record in the U.S., causing centres around the nation to review their procedures.

University Hospitals said two weeks ago that the storage tank was having trouble for weeks and that an alarm system had been turned off when the tank's temperature began to rise.

In a letter to patients, the hospital described how the tank was undergoing preventive maintenance because of a problem with a system that automatically fills the liquid nitrogen that keeps the embryos frozen.

The clinic was planning to transfer the embryos to another tank and said it was manually filling the tank with nitrogen by pouring it into the top.

Custom Biogenic Systems, which is based in Bruce Township near Detroit, said last past week that it provided the clinic instructions on how to thaw the storage tank and that it was not designed to be filled manually from the top.

The tank's manual says filling the tank from the top "will cause liquid nitrogen to come into contact with the stored samples," the company said. It also said the storage tank isn't designed to monitor liquid nitrogen that is poured into the top.

A message seeking comment was left Tuesday with University Hospitals, which has said about 950 patients were affected, is facing several lawsuits.

Couples who had stored their eggs and embryos at the clinic had been trying for years to get pregnant, suffered multiple miscarriages or undergone cancer treatments that destroyed their fertility.

Custom Biogenic Systems also said it didn't have anything to do with the remote alarm system that had been turned off. It said the tank functioned properly by indicating a high-temperature condition and activating a local alarm.

University Hospitals has said it doesn't know who shut off the remote alarm, which should have alerted staff to changes in the storage tank's temperature on the weekend of March 3 when no one was at the lab.

___

Seewer reported from Toledo.

News from © The Associated Press, 2018