A Chinese headmaster has been fired after a secret stack of crypto-currency mining machines was found connected to his school's electricity supply.

Axar.az reports citing Foreign media that teachers at the school in Hunan became suspicious of a whirring noise that continued day and night, local media report.

This led to the discovery of the machines, which were mining the crypto-currency Ethereum.

They racked up an electricity bill of 14,700 yuan (£1,600).

The excessive electricity consumption had previously been reported to the headmaster, Lei Hua, but he reportedly dismissed it as being caused by air conditioners and heating devices.

Mining crypto-currencies such as Bitcoin and Ethereum involves using computers, usually specialised "mining machines" connected to the currency network.

By providing computing power for validating transactions on that network, mining-machine owners are rewarded with newly generated coins, making it a potentially lucrative exercise - especially when done at scale.