(AP) — One of China’s biggest bitcoin exchanges says it will end trading after news reports regulators have ordered all Chinese exchanges to close caused the price of the digital currency to plunge.

BTC China said on its website it will “stop all trading business” on Sept. 30. The exchange said it was acting “in the spirit of” a central bank ban last week on initial coin offerings but gave no indication it received a direct order to close.

The central bank has not responded to questions about the currency’s future in China.

There was no immediate word from other Chinese bitcoin exchanges about their plans.

Bitcoin’s value tumbled 15 percent on Thursday to about $3,300. The famously volatile currency has shed about a third of its value since Sept. 1 but is up from about $600 a year ago.

Bitcoin surged in popularity in China last year as its price rose. Trading dwindled after regulators tightened controls and warned the currency might be linked to fraud.

Two business newspapers reported Thursday regulators in Shanghai, the country’s financial center, gave verbal instructions to Chinese bitcoin exchanges to close.

Bitcoin is created and exchanged without the involvement of banks or governments. Transactions allow anonymity, which has made bitcoin popular with people who want to conceal their activity. Bitcoin can be converted to cash when deposited into accounts at prices set in online trading.

A Chinese business news magazine, Caixin, said at one point up to 90 percent of global trading took place in China.