Chinese investors are pumping up bitcoin again, sending prices up nearly 16% in the past four days, just two years after the country was at the center of a boom and bust in the crypto-currency.

The four-day surge in bitcoin since Friday has added $1.2 billion in market capitalization for all bitcoin in circulation, according to data from blockchain.info. On Monday, prices moved up as high as $525.49 per bitcoin, though that’s still well below the all-time high of about $1,151 in November 2013.

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