Late Saturday the temperature rose in a tank of liquid nitrogen, where frozen eggs and embryos were stored, damaging their viability. Some samples date to the 1980s.
A University Hospitals spokeswoman said the security increase is because of the, "emotional nature of the situation". It is unknown whether the problem was caused by a human error or mechanical failure.
Patients typically pay about $12,000 without insurance for in vitro fertilization.
The only way to find out if the samples are still viable is to thaw and implant them, the hospital told the the Cleveland Plain Dealer.
"At this point, we do not know the viability of all of the stored eggs and embryos, although we do know some have been impacted", said Patti DePompei, president of UH Rainbow Babies and Children's Hospital, in a video posted Thursday on Facebook. Some specimens that were already thawed since Sunday for planned procedures were found not to be viable, the Plain Dealer reported. The incident could have affected over 2100 frozen eggs and embryos say the sources.
Staff members are working with experts to "better understand the cause of this temperature fluctuation and ensure that it doesn't happen again", she said.
The incident comes as a growing number of women choose to freeze their eggs due to illness, or because they are concerned that the quality and quantity of their eggs will drop over time.
The storage tank had off-site monitoring and an audible alarm that would alert staff to such a temperature change. Some of these eggs and embryos have been stored in there for decades. Per a University Hospitals statement cited by News 5 Cleveland, the facility has "initiated contact with all of our patients", and a call center has been set up so patients can set up meetings with doctors.
"Our hearts go out to the patients who have suffered this loss", Sean Tipton, chief policy officer at ASRM, told NBC News.