(Bloomberg News) U.S. investigators of bankrupt MF Global Holdings Ltd. have yet to determine after four months of probing whether enough evidence exists to pursue a criminal case, a person with knowledge of the matter said.

When the broker-dealer run by former Goldman Sachs Group Inc. Co-Chairman John Corzine filed for bankruptcy Oct. 31, federal prosecutors in Chicago had a grand jury issue a flurry of subpoenas, said the person, who declined to be identified because they aren't authorized to speak publicly.

Investigators from the Commodity Futures Trading Commission, Federal Bureau of Investigation and other agencies have been analyzing events that occurred before the bankruptcy, when as much as $1.6 billion in client funds went missing, said the person.

After grand jury subpoenas were issued by Patrick Fitzgerald, the U.S. Attorney in Chicago in the days after the firm's collapse, federal investigators turned their focus to reviewing the mountains of documents on thousands of transactions worth hundreds of millions of dollars, the person said. Since that time, no decision has been made about whether charges will be filed against MF Global officials, they said.

In fact, no determination has been made whether Fitzgerald or U.S. Attorney Preet Bharara in New York would lead any prosecution, the person said. Randall Samborn, a spokesman for Fitzgerald in Chicago and Carly Sullivan, a spokeswoman for Bharara's office, declined to comment.

MF Global, one of the largest clearing brokers at CME Group Inc., used about $700 million of customer funds to "meet liquidity issues" at its broker-dealer in the days prior to the bankruptcy, according to a timeline of events released by CME, the world's largest futures exchange.

CME said it received subpoenas in November from the Chicago federal grand jury investigating MF Global's collapse, as well as the CFTC, according to a Feb. 28 regulatory filing.

The grand jury subpoena was issued the day after MF Global collapsed. The CFTC subpoena came the day after that, CME said.

CME Group, which had auditing authority over the failed futures broker, was asked by the grand jury to produce information and witnesses in connection with the investigation, the Chicago-based company said in a regulatory filing.

While Fitzgerald's office sent subpoenas early in the process, no more have been issued, the person said. The FBI opened up a formal inquiry in early November, said the person.