Research samples collected over decades at a Swedish medical university were destroyed when a freezer malfunctioned during the Christmas holidays, the institute has said.

The samples were stored in tanks cooled with liquid nitrogen, at a temperature of -190C, at Karolinska Institutet (KI) in Stockholm.

Matti Sällberg, dean of KI’s southern campus, said on Monday: “It happened at possibly the absolute worst time imaginable in Sweden, just one day before Christmas Eve.”

“Those worst affected are those researching leukaemia, they have gathered samples from patients over as much as 30 years,” he added.

An internal investigation has been launched at the university and despite there being no indication of sabotage, the incident has also been reported to police.

Sällberg said: “Currently there is no indication that it was due to outside influence but the police report was done to cover all bases.”

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