The U.S. Commodity and Futures Trading Commission (CFTC) has reportedly subpoenaed four cryptocurrency exchanges in a bid to obtain their trading data as part of an investigation into market manipulation.

According to a The Wall Street Journal report on Friday, the financial market regulator is demanding comprehensive trading data from Bitstamp, Coinbase, itBit and Kraken, which altogether serve as a base for the bitcoin futures price listed by CME Group.

Citing sources familiar with the matter, the WSJ said the subpoena was issued because the CFTC was “upset” that CME had not succeeded in negotiating with the exchanges for access to their trading data.

The exchanges rejected the request initially, calling it “intrusive,” according to the report. Although the exchanges in the end did submit some trading data, their compliance only came after CME had compromised by limiting the range of its access from a full-day’s activity to just a few hours, and to limited market participants.

According to the report, the failure irked the CFTC, which supervises CME and gave it the green light in December 2017 to list bitcoin futures.

“All participating exchanges are required to share information, including cooperation with inquiries and investigations,” said a CME spokeswoman in the report.

News of the investigation first emerged on May 24, indicating that the U.S. Department of Justice had launched a probe into illicit trading practices in the crypto market in conjunction with the CFTC.

According to that report, the government agencies are investigating traders that may have influenced the bitcoin market through old-school tactics such as sending large numbers of fake orders.

Bitcoin and US dollar image via Shutterstock