Samples collected for decades by researchers at a prestigious Swedish medical university were destroyed after a freezer malfunction during the Christmas holidays, the university said on Monday.
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The incident was reported to police, the university added.
The samples were stored at a temperature of minus 190 degrees Celsius in tanks cooled with liquid nitrogen at the Karolinska Institute (KI), a recognized medical university in Stockholm.
KI is the seat of the Nobel Assembly, which is responsible for selecting the Nobel Prize winner in Physiology or Medicine.
Between December 22 and 23, the supply of liquid nitrogen to 16 cryogenic tanks was interrupted.
While the tanks can operate without supplemental liquid nitrogen for four days, they were without supplemental liquid nitrogen for five days, resulting in the destruction of samples from multiple institutions.
“This happened at the worst time imaginable in Sweden, just one day before Christmas Eve,” Matti Sallberg, dean of KI's south campus, told AFP.
Some media reported that the estimated value of the lost samples was about 500 million crowns (US$47 million).
Mr Sallberg said no official estimate had been made of the value of the lost samples, but it was easily in the millions.
“Those most affected are those who research leukemia because they have collected patient samples over a period of up to 30 years,” said Sallberg.
An internal investigation was launched at the university and although there was no evidence of sabotage, the incident was also reported to the police.
“There is no evidence yet that the incident was due to external influence, but a police report is being prepared to cover all hypotheses,” Mr Sallberg said.
The samples were for research purposes only and their loss should not impact the care of current patients, but they should be used for future research.
“These are samples that have been the subject of extensive study and there have been plans to do more,” Mr Sallberg said.