Apple Inc. (AAPL) removed Blockchain, an application for iPhones used to send and receive Bitcoins, from its App Store, the developer of the program said.

Blockchain.info, the developer of the software, received an e-mail from Apple saying that the app was withdrawn “due to an unresolved issue,” Nicolas Cary, chief executive officer of the London-based company, said.

As a virtual currency, Bitcoins exist only as software and transactions are completed via computing devices. With merchants from car dealers and Web stores accepting the digital money, mobile apps have become a popular commerce tool. At the same time, some governments including China and India have questioned Bitcoin’s legal status. Since Apple requires apps to be legal in all territories that they’re offered, many Bitcoin-related programs for Apple’s iOS mobile software don’t offer the ability to send money.

“We’ve been there two years,” Cary said in an interview. “What did they just discover that is now unresolved?”

Tom Neumayr, a spokesman for Cupertino, California-based Apple, declined to comment.

Blockchain, which lets holders view their Bitcoin balance in online wallets the company maintains, has been downloaded by 120,000 users, Cary said.

Applications to monitor the price of Bitcoin or access related news are still available on the store. Coinbase Inc. and Gliph Inc., two San Francisco-based startups that let users transact, are also no longer on Apple’s App Store.

Fred Ehrsam, the CEO of Coinbase, said the app was removed in November. Rob Banagale, CEO of Gliph, said Apple allowed the the company’s app on the store, provided it removed the ability to send and receive Bitcoins.