After detecting an unusual spike in energy consumption, Iranian authorities seized nearly a thousand computers being used to mine cryptocurrency, according to the country’s state media.

Authorities discovered two bitcoin farms operating in abandoned factories in Yazd province, which caused a seven percent spike in the country’s power consumption this month. Iran’s central bank banned cryptocurrencies last year, citing concerns over money laundering. According to RadioFreeEurope, officials have said that the practice is making the local power grid “unstable,” and warned that people engaging in the practice could be cut off.

Cryptocurrency is “mined” as high-powered computers solve mathematical problems, a task that requires considerable power. Iran subsidizes its power, keeping prices low, which appears to be one reason why miners have been operating in the country. Access to cryptocurrency also appears to be helping residents evade US-imposed banking sanctions.