Tesla Inc. shares fell in premarket trading, plunging below the level at which the electric-car maker entered the S&P 500 in December.

The stock dropped as much as 9% to $650 in New York, after falling a similar amount on Monday. Through Monday’s close, the stock was down 21% from its Jan. 25 record intraday high.

Tesla’s early-week decline amid a wider market sell-off also was fueled in part by Chief Executive Officer Elon Musk’s comments over the weekend that the prices of Bitcoin and smaller rival Ether “do seem high.”

The concerns over the value of the cryptocurrency helped erase some of Bitcoin’s gains, which had rocketed to new highs after Tesla announced two weeks ago it added $1.5 billion in Bitcoin to its balance sheet.