The price of bitcoin swung wildly Thursday, rising to more than $19,000 only to fall sharply within minutes.

Around 10:40 a.m. Pacific Time, one bitcoin was valued at $15,872, according to Coinbase; it briefly surged above $19,000 earlier in the day.

Last week, the price of a bitcoin topped $10,000 for the first time.

The price swings are occurring not long before bitcoin starts trading on two established U.S. exchanges.

The price swings are occurring just as the trading community prepares for bitcoin to start trading on two established U.S. exchanges.

T are fresh concerns about the security of bitcoin and other virtual currencies after NiceHash, a company that mines bitcoins on behalf of customers, said it is investigating a breach that may have resulted in the theft of about $70 million worth of bitcoin.

In Japan, after the failure of a bitcoin exchange called Mt. Gox, laws were enacted to regulate bitcoin and other virtual currencies.

The blockchain prevents rogues from spending the same bitcoin twice, and the miners are compensated for their efforts with the occasional bitcoin.

10:55 a.m.: This article was updated to reflect swings in bitcoin’s price and the perspective of the Futures Industry Assn.