The great cryptocurrency crash of 2018 is heading for its worst week yet.

Bitcoin sank toward $4,000 and most of its peers tumbled on Friday, extending the Bloomberg Galaxy Crypto Index’s weekly decline to 25 percent. That’s the worst five-day stretch since crypto-mania peaked in early January.

After an epic rally last year that exceeded many of history’s most notorious bubbles, cryptocurrencies have become mired in a nearly $700 billion rout that shows few signs of abating. Many of the concerns that sparked the 2018 slump — including increased regulatory scrutiny, community infighting and exchange snafus — have only intensified this week. Even after losses exceeding 70 percent for most virtual currencies, Oanda Corp.’s Stephen Innes has yet to see strong evidence of a capitulation that might signal a market bottom.

“There’s still a lot of people in this game,” Innes, head of trading for Asia Pacific at Oanda, said by phone from Singapore. If Bitcoin “collapses, if we start to see a run down toward $3,000, this thing is going to be a monster. People will be running for the exits.”

Innes said his base case forecast is for Bitcoin to trade between $3,500 and $6,500 in the short term, with the potential to fall to $2,500 by January.

The largest cryptocurrency retreated 4.4 percent to $4,237 at 11:31 a.m. in Hong Kong, according to Bloomberg composite pricing. Rivals Ether, Ripple and Litecoin all declined at least 4.8 percent. The market value of all cryptocurrencies tracked by CoinMarketCap.com sank to $138 billion, down from about $835 billion at the market peak in January.

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