Samples collected over decades by researchers at Sweden’s prestigious Karolinska Medical University were destroyed after freezers malfunctioned during the Christmas holidays, the institution announced on Monday and reported the incident to police, AFP reported.

The samples were stored at a temperature of -190 degrees Celsius in tanks cooled with liquid nitrogen at the Karolinska Institute, a well-known medical university in Stockholm, writes News.ro. Karolinska also hosts the Nobel Assembly, which selects the winner of the Nobel Prize in Medicine.

In the period from December 22 to 23, the supply of liquid nitrogen to 16 cryogenic tanks was stopped. Although the tanks can operate for four days without supplemental liquid nitrogen, they were deprived of the substance for five days, resulting in the destruction of samples from several facilities.

“It happened at the worst possible time in Sweden, just the day before Christmas Eve,” Matti Salberg, dean of Karolinska Institutet’s south campus, told AFP.

“Those involved in leukemia research were the most affected”

Some media reported that the estimated value of the lost samples is around 500 million kroner ($47 million). Zallberg said no official estimate has been made of the cost of the lost samples, but it is easily several million.

“Leukemia researchers were the most affected because they collected samples from patients over a period of up to 30 years,” Salberg said.

The university launched an internal investigation and, although there were no signs of sabotage, the incident was also reported to the police. “At the moment there is no indication that the incident was due to external influence, but a police report is being drawn up for all hypotheses,” said Matti Sahlberg.

All samples were for research purposes only and their loss will not affect ongoing patient care. But they will be used for future research.