Bitcoin’s volatile week-long slide saw it plummet to below the $40,000 mark on Wednesday as news of further curbs on digital currency transactions in China added to earlier concerns sparked by Tesla boss Elon Musk’s tweets.

Bitcoin, the world’s most popular cryptocurrency, dropped nearly 9% to as low as $38,940.04, even slipping below a key 200-day moving average. The currency is now down 40% from the year’s high of $64,895.22 on April 14.

Ether, the coin linked to the ethereum blockchain network, fell around 15% to $2,875.36.

The dwindling of the 2 most traded digital currencies was sparked last week by Musk’s reversal on Tesla accepting bitcoin as payment, followed by other tweets that fueled confusion over whether the carmaker had shed its holdings of the cryptocurrency.

Beijing’s announcement on Tuesday that it is barring payment companies and financial institutions from providing services related to digital currency transactions, coupled with a warning to investors against speculative crypto trading, seemed to have exacerbated the selling.