LOS ANGELES >> A freezer malfunction resulted in the loss of blood stem cells from 56 child patients at Children’s Hospital Los Angeles, but no child’s health is in jeopardy due to the incident, the hospital said in a statement on its website.

Patients and their families were notified in letters sent earlier this month and a phone line was established for families with questions, the statement said.

“We apologize for any distress or confusion that this has caused our patients and their families,” the hospital said.

The hospital said it also apologized after learning that the letters informing the families were addressed to the patients.

“These blood stem cells, all of which were collected from patients, were in long-term storage,” the statement said. “We routinely collect cells early in a child’s course of oncology therapy for possible future use. When excess cells are not needed, they remain in storage in the unlikely event that they could become helpful in the future.”

The hospital said the failure involved freezer temperature sensors and that safeguards in place at the time were “insufficient.”

The freezer has been replaced, the sensor monitoring and alert system has been upgraded, power sources have been double checked, maintenance has been increased, and engineering staff are being trained on the new system, the hospital said.

Chief medical officer James Stein told the Los Angeles Times that all but one patient had gone through initial therapy and that patient did require recollection of stem cells.

Collecting stem cells again from the patients would only be recommended if needed in the event of a relapse, Stein said.

“We think that’s going to be incredibly unlikely so we wouldn’t ask anyone to do that in advance,” he said.

Children’s Hospital Los Angeles is a nonprofit institution founded in 1901 and located in East Hollywood.