The International Monetary Fund said Friday it may be impossible to identify who mounted a cyber attack on its computer files in May, after a Bloomberg report suggested it was China.

"We are not prepared to finger-point at this time. We also may never know who perpetrated this cyberattack," an IMF spokesman said in a brief statement to the media.

The IMF spokesman said he was responding to questions related to a story published Friday by Bloomberg on the Fund's cyberattack.

The Bloomberg article said investigators of a "very major hacking attack" against the IMF determined that Chinese cyber spies were behind it, citing sources close to the investigation who were not authorized to speak about it.

According to the sources, evidence pointing to China includes "an analysis of the attack methods" and "the electronic trail left by hackers."

The IMF revealed on June 8 it had been the victim of a cyberattack, saying documents had been copied. The nature of the information stolen has not yet been made public.

"Our efforts to assess the impact and extent of the attack is continuing," said the spokesman, who was not identified.

On July 12 a former senior Chinese central banker, Zhu Min, was nominated to be an IMF deputy managing director, elevating China's stature and influence in the world's crisis lender.

The 187-nation Fund and China remain at odds over certain economic issues, particularly its currency, the yuan.

In an annual report on the Chinese economy published Wednesday, IMF economists estimated that the yuan was undervalued by 3.0 percent to 23 percent compared to its major trade partners.

China said it disagreed with that IMF view.