An alarm system turned off on a fertility clinic storage tank that had been malfunctioning for weeks led to a failure that likely ruined more than 4,000 eggs and embryos, double what the clinic first thought, it said Tuesday.

The clinic run by University Hospitals in suburban Cleveland does not know who shut off the alarm or why it happened, according to a letter sent to its patients.

The alarm should have alerted staff when the storage tank’s temperature began to rise on the weekend of March 4 when no one was at the lab.

‘‘We don’t know who turned off the remote alarm nor do we know how long it was off, but it appears to have been off for a period of time. We are still seeking those answers,’’ the letter said.

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 US, causing centers around the nation to review their procedures. So far, there are no known connections between the failures.

ASSOCIATED PRESS