A freezer failure at the Harvard Brain Tissue Resource Center damaged one-third of the world's largest donated brain collection for autism research.

A total of 93 donated brains were damaged at McLean Hospital in Belmont, Mass., 54 of them earmarked for autism research through Autism Speaks. Harvard spokesperson, Adriana Bobinchock, said an investigation is underway to determine how the freezer failure occurred.

The freezer's temperature failed in late May, and alarms that normally indicate rising temperatures did not sound.

Dr. Francine Benes, director of the Harvard Brain Tissue Resource Center, told the Boston Globe that the damaged brains were a "priceless collection." While foul play cannot totally be ruled out at this time, Bobinchock said that after reviewing surveillance footage and other safety measures, foul play is not likely.

Scientists are currently conducting tests to see if DNA in the damaged brains is intact and can be used for further genetic research. Bobinchock said, however, that "it is unclear whether the samples will be compatible with the full-range of the needs of neuroscientists."

Thirty-two of the brains had been bisected, with one hemisphere placed in formalin (a formaldehyde liquid) and one half put in the freezer. The brains contained in the formalin remain available for all research projects.

Autism Speaks did not return ABC News' requests for comment, but according to an open letter from the organization's Chief Scientific Officer Dr. Geri Dawson, many of the damaged samples had already been used in many clinical studies.

"We are confident that we can maintain the momentum of scientific studies based on brain tissue," Dawson wrote.

There are more than 3,000 donated brains currently in the Brain Bank's collection. It is the largest and oldest federally-funded brain bank in the U.S. In addition to autism, the Brain Bank collects brain tissue for the research of bipolar disorder, schizophrenia, Parkinson's and Alzheimer's.

Bobinchock said two secure locked doors that are under 24-hour video surveillance protect the brains. Benes told the Boston Globe that the freezer was estimated to have been off three days before someone discovered the warmer-than-normal temperatures. The newspaper reported that the Brain Bank has been accepting donations from people with autism for about 20 years, so it will likely take several years to replace the damaged collection.

"This is definitely a blow to the speed of progress, given that donations occur over a period of years and it takes time to amass a large sample," said Lori Warner, director of HOPE Center for Autism. "This type of brain research is unique in that it's actual physical evidence of any differences or changes in the brains of the patients compared to controls who do not have autism."

Dawson noted that brain donations are precious to the research and understanding of a myriad of health conditions.

"We want to ensure that this unfortunate and rare incident will not negatively affect donations in the future," Dawson said. "We remain committed as ever to conducting research that will uncover the causes of autism and allow us to develop more effective treatments."