Police in Hebei, a province in Northern China, have seized 6,890 bitcoin mining hardware units that were illegally used to mine cryptocurrencies, reported China Central Television (CCTV), the predominant public television broadcaster in mainland China.

According to the CCTV report, police in the country have launched a nationwide criminal investigation into electricity theft and found that using stolen electricity to power bitcoin mining rigs have been rampant over these years.

Among those efforts, police in Tangshan, Hebei province, have so far seized 52 high-power transformers and 6,890 bitcoin mining machines in a local investigation started from last April, which has led to multi-million dollar worth energy losses.

According to the police, a single bitcoin mining machine operating around the clock can consume up to 40 kWh in a day. Suppose an average family of three consumes 6 kilowatt-hours of electricity per day, the 6,890 bitcoin mining machines confiscated could consume as much electricity as around 46,000 households consume in a day.

Prior to it, around 4,000 bitcoin-mining machines hidden in 12 hideouts in Zhenjiang in China’s eastern province of Jiangsu province have been confiscated by police this July. Investigators said they found the computers after getting a tip from a local power company about abnormal electricity usage in the area.

China is a known crypto mining giant, reportedly wielding 66% of global bitcoin hash rate despite its rigid stance towards cryptocurrencies. Many bitcoin mining farms are based in China due to the massive surplus of cheap electricity especially the abundant hydropower in southwestern China.

Crypto mining is not ruled illegal in the country. It is those illegal activities involving stealing electricity to fuel the mining machines and crypto mining farms built with no approval that are cracked down, which in effect helps regulate the bitcoin mining industry.

This April, China’s state planner planned to classify crypto mining into the industry that shall be eliminated immediately, saying it’s resource wasteful, while six months later in November, the authority has removed bitcoin mining from eliminated industry following the country’s president Xi Jinping’s blockchain endorsement.