(Reuters) – Three of the top four most actively traded U.S. stocks on Monday were all either riding a cryptocurrency-fueled surge, or pulling back from one.

Shares of Digital Power Corp, which on Monday promised a progress report on the cryptocurrency initiative of its Coolisys Technologies unit next week, had a market value of just $12.8 million on Friday.

That had more than tripled to just north of $40 million by early afternoon in New York.

Coolisys, which targets “specialized products and services not likely to be commoditized”, in August partnered with PoW Digital Mining to develop a tech and services portfolio for digital mining and cryptocurrency.

Its moves are typical of the sort of baby steps being taken into the area by the companies benefiting most from a surge in bitcoin that has beaten other asset classes hollow this year.

IP licensing company Marathon Patent Group’s shares were also up about a third, having more than quadrupled in value in two otherwise thin trading sessions either side of the Thanksgiving holiday.

That brought its stock to highs not seen in a year, its market value to nearly $50 million and made it the third most traded U.S. stock.

The company said on Nov. 2 it would buy cryptocurrencies miner Global Bit Ventures Inc and last week announced plans to give an update on the deal in an investor call on Monday after markets close.

Bitcoin has enjoyed a stellar year, outdoing all other asset classes in growth. It soared to a record high of $9,721 on Monday – a tenfold increase in its value since the start of January.

The market capitalization of all cryptocurrencies – their price multiplied by the number of coins released into the system – also topped $300 billion for the first time, according to industry website Coinmarketcap.

The staggering price increases, however, have prompted warnings from central bankers, bank chief executives and other investors that it has reached bubble territory.

Mobile payments company Square Inc, whose stock has gained nearly a fifth since it launched bitcoin purchases and sales on its app on Nov. 15, fell about 13 percent on Monday after brokerage BTIG said the rally was overdone.

Riot Blockchain Inc was down by about a quarter on Monday after gaining 240 percent since it said at the start of November it would buy 1,200 bitcoin mining machines.

As recently as early October, the company was called Bioptix Inc and dealt with IP licenses related to veterinary products.