Tencent’s accelerating sell-off could get a lot worse if the stock fails to hold above its key support level.

There’s a risk that will happen on Thursday: Asia’s biggest stock was down 0.6% in Hong Kong as of 1.03pm local time, despite an otherwise upbeat stock market.

Tencent is now trading below the key level of HK$320 that supported its shares on three occasions this year. The stock has lost about 20% since a peak in April, equivalent to some US$93-billion in market value.

While the shares have been stuck in a downtrend for months, selling was particularly aggressive on Wednesday despite no apparent trigger. Theories circulating round some trading floors included souring sentiment from investors in China, as well as concern that Tencent’s decision to air National Basketball Association games may backfire.

Adding to jitters this week was a local media report that China is considering revising a law to control young people’s online gaming activities — a business that remains one of Tencent’s most profitable. The Internet giant will report third quarter earnings on 13 November. — Reported by Jeanny Yu, with assistance from Elena Popina and Cindy Wang, (c) 2019 Bloomberg LP