White House press secretary Sarah Sanders said Thursday that officials are monitoring the digital currency bitcoin for possible regulation.

"I know this is something that's being monitored by our team here," Sanders said at the daily White House press briefing.

Sanders said that Tom Bossert, a presidential adviser on national security issues, mentioned bitcoin in a meeting this week.

"It's something he's keeping an eye on and we'll keep you posted when we have anything further on it," Sanders said.

The so-called cryptocurrency, established in 2009, has expanded in mainstream acceptance from origins as a libertarian fascination popular for buying drugs on darknet markets.

Bitcoin fluctuates in value, and people who gain income are supposed to pay taxes. Fewer than 900 people, however, reported gains between 2013 and 2015, Bloomberg reported.

Massive gains are possible for early investors. A Norwegian man named Kristoffer Koch, for example, purchased 5,000 bitcoins in 2009 for $27. In 2015, after he remembered the purchase, they were worth nearly $900,000. Their current value is more than $47 million, according to Google Finance data.

The are many other less-popular digital currencies, including litecoin and monero.

The government is moving to crack down on possible tax avoidance as digital currencies gain wider use. The Internal Revenue Service won a court ruling this week for records from the company Coinbase, a popular platform for buying bitcoin.

Bossert did not immediately respond to a request for additional information on what the White House is considering as part of its monitoring.