Police in Tianjin have confiscated 600 bitcoin mining computers after the local power grid reported abnormal electrical consumption.

According to Xinhua News Agency, an electrical line monitored by the power company in Tianjin recently saw a sudden increase in line losses of up to 28 percent during peak hours.

Investigators said they found that an electrical junction box for a power user's electricity meter had been bypassed, which is a typical way to escape billing.

Bitcoins are a virtual currency used to buy other currencies, products and services online. Bitcoin mining uses algorithms to verify transactions, and miners earn bitcoins in exchange. Powerful computers are used to calculate algorithm outcomes before other miners, so bitcoin miners usually seek locations with easy access to cheap electricity. Basically, the fastest computer wins.

It was estimated that the monthly electrical charge for 600 such computers would be hundreds of thousands of yuan.

Online exchanges of virtual currencies have been closed in China.

Local police said that one person was detained and five others are under investigation. Eight high-powered cooling fans were seized.

In January, Beijing police cracked a case involving the theft of 100 bitcoins worth more than 2 million yuan ($316,000) at the time, according to media reports.

The suspect, surnamed Zhong, an operations maintenance engineer at a Beijing-based internet technology company, embezzled bitcoins from the company. He was detained in March and is awaiting trial.