Trading on mainland China’s two stock exchanges was halted on Thursday (Jan. 7) morning after share indexes crashed for the second time in a week. The markets will remain closed for the rest of the day.

Share markets opened at 9.15am local time, but trading was soon halted for 15 minutes by automatic circuit breakers which are triggered when indexes fall by 5%. A whole day suspension of trading became automatic when the drop exceeded 7% at 09:59 local time.

On Monday (Jan. 4), the first business day of the new year saw a similar halt. The market plunged by 7% following the publication of an important index indicating a weakening business outlook in the world’s second largest economy. That spooked stock markets around the globe into falls on Monday. China’s regulators stepped in with policy and liquidity measures and a degree of calm returned on Tuesday (Jan. 5).

This time the crash on Thursday may have been provoked by the rapid weakening of the Chinese currency, which is now close to a five year low against the U.S. dollar. According to the official China Foreign Exchange Trading System the Chinese Yuan or Renminbi had a central parity rate of RMB6.5646 per dollar. That compares with an exchange rate of RMB6.15 to the dollar only a few months ago.

Weakening to this level risks causing a flight of capital out of China. And it also stokes the risk of political tensions with the U.S., where China’s currency policies have been regularly criticized by politicians and presidential hopefuls.

The separately-regulated stock market in Hong Kong remains open. At 11am local time it was down 2.7% with the Hang Seng Index at 20,413.

Media and entertainment stocks in China were badly hit by the Thursday collapse. Shares of Wanda Cinema Line were down 8.99% at RMB96.4. Huayi Brothers Media was down 10% at RMB34.36. Enlight Media as down 9.99% at RMB24.87. Huace was down 9.99% at RMB24.41. DMG was down 10% at RMB32.88.

Those traded in Hong Hong were also punished. At 11am local time, Alibaba Pictures Group shares were down 6.12% at HK$1.84. Fosun International was down 5.54% at HK$10.9. Tencent was down 2.67% at HK$142.20. IMAX China was down 8.19% at HK$45.4. Orange Sky Golden Harvest was down 6.25% at HK$0.6.