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A cleaner destroyed decades of "groundbreaking" work by shutting off a lab freezer containing key samples over an "annoying" alarm sound, US lawyers have claimed.

A sign explained how to mute the beep, but a breaker was reportedly switched off after a reading error.

Samples stored at -80C (-112F) were left "unsalvageable", causing $1m in damages, lawyers said.

The lab's school is suing the cleaner's employer for improper training.

The company held a $1.4m (£1.1m) contract to clean the Rensselaer Polytechnic Institute in Troy, New York back in 2020 which is when the alleged incident happened,

Research on photosynthesis, headed by Prof KV Lakshmi, had the potential to be "ground-breaking" in furthering solar panel development, a lawyer for the institute wrote.

A few days before the freezer was turned off, an alarm went off to alert a 3C temperature rise. Though the fluctuation could have been catastrophic, Prof Lakshmi "determined that the cell cultures, samples and research were not being harmed," the legal case read.

Due to Covid restrictions at the time, it would take a week before any repairs could begin.

In the meantime, a sign on the freezer's door read: "This freezer is beeping as it is under repair. Please do not move or unplug it. No cleaning required in this area.

"You can press the alarm/test mute button for 5-10 seconds if you would like to mute the sound."

But days after the alarm started sounding, the cleaner turned off the circuit breaker providing electricity to the freezer.

The majority of specimens that were meant to be kept at -80C were "compromised, destroyed and rendered unsalvageable, demolishing more than 20 years of research", according to the legal case.

A report filed by public safety staff at the institute said the cleaner thought they were flipping the breaker on when they actually turned it off, the New York Post reported.

The temperature had allegedly risen by 50 degrees to about -30C by the time researchers discovered the error.

Lawyer Michael Ginsberg told NBC News that the cleaning employee heard "annoying alarms", and lawyers that interviewed him reported "he still did not appear to believe he had done anything wrong, but was just trying to help."

The institute's legal team says the company that employed the cleaner failed to adequately train their employee. The company has not yet commented.