A principal who set up a secret cryptocurrency mining operation in his school has been sacked after teachers noticed a whirring sound coming from the computer room.
According to the BBC, Lei Hua, a headmaster at Puman Middle School in Chenzhou, Hunan Province, was let go after he was found to be mining ethereum on school grounds.
Hua managed to rack up a 14,700 yuan ($3109) electricity bill after using the school's power to run the mining machines day and night.
Hua began mining the cryptocurrency at home in a bid to make some extra money on the side, but realised the device was chewing through 21 kilowatt-hours of electricity a day.
He moved the computer to the school, and added a further seven "miners" to his operation.
Eventually, the school's deputy principal Wang Zhipeng also joined in, buying a ninth machine himself and also running it on the school grounds.
Hua was sacked last month, while Zhipeng was allowed to keep his job after being given an official warning.
The BBC claimed Hua had previously been warned about the school's unusually high power bills, which he claimed was due to cooling and heating devices used in classrooms.
But eventually, teachers noticed a constant whirring noise, which led to the discovery of the machines which were installed in a computer room between summer 2017 and summer 2018.
Apparently, the mining scheme also overloaded the school's computer network and caused internet connections to slow down, which affected teachers' ability to do their jobs.
According to Caixin Global, cryptocurrency "miners" work by solving "the mathematical puzzles that power a cryptocurrency's network".
They are then awarded "coins" of the virtual currency, which can be converted to "hard" currencies.
However, the process also requires a great deal of electricity, which is how Hua and Zhipeng were caught.
It is not known how much the men made from their scheme, although Chinese media revealed their profits had been seized by China's disciplinary commission.
Cyber-security expert Matthew Hickey told the BBC the educators' scheme would have been obvious.
"The noise and heat of nine actively running mining machines would have been very noticeable," he said.