A court-appointed investigator probing some of the allegations of fraud that led to Refco Inc.'s collapse last year has demanded the employment records of four employees of Grant Thornton LLP.

Grant Thornton served as the commodity brokerage's accountants before the crash.

The investigator, Joshua Hochberg, said in papers filed with the U.S. Bankruptcy Court in Manhattan that the records could have a significant impact on his investigation. He didn't discuss the allegations he is exploring, but his request for records included the personnel files of Mark Ramler, who led the Grant Thornton team that audited Refco.

Ramler, who works in Grant Thornton's Manhattan office, wasn't available to comment Monday. Grant Thornton, in a statement Monday, said it actually helped expose Refco's alleged fraud.

Hochberg said Ramler, who previously worked for the accounting firm Arthur Andersen, brought Refco to Grant Thornton as a new client around August 2002. He also said he had reason to believe that Grant Thornton also served as tax accountants to Phillip Bennett, Refco's chief executive at the time of the collapse.

Refco crashed into bankruptcy in October 2005 amid allegations that Bennett had hidden $430 million in bad debt. Shortly after, the company's stockholders and bondholders filed a class-action lawsuit against Bennett and more than a dozen other defendants it said were responsible for the company's collapse.

Grant Thornton is a defendant in that lawsuit, which accuses the accounting firm of having repeatedly failed to detect huge, nine-figure sham transactions conducted by Bennett and others. The lawsuit contends that the circumstances under which Refco's business moved to Grant Thornton from Arthur Andersen was partly responsible for that.

Former Andersen partner Mark Ramler, Andersen's engagement partner for Refco, moved to Grant Thornton and brought the Refco account with him, the lawsuit said. This new business was a major triumph for Grant Thornton, which had picked up the crumbs of Andersen's collection of former clients as it watched the (now) Big Four accounting firms take the overwhelming majority.

Grant Thornton was thus motivated to restrain its approach to auditing Refco in order to minimize the risk that the company _ the crown jewel former Andersen client _ would take its business elsewhere, the lawsuit said. Willful blindness to Refco's false and misleading financial reporting was the result.

In a statement Monday, Grant Thornton said it was anything but blind.

We notified Refco of deficiencies in their internal controls which were disclosed during their public offering, as well as raising questions with management which eventually led to the discovery of the problems, the firm said.

Unfortunately, there was a well-orchestrated fraud carried out by senior management, hidden well enough to also evade numerous other detailed financial inspections performed by many of the well-respected financial institutions in the country, its statement added.

Hochberg, the investigator who sought the employment records of Ramler and three other current or former Grant Thornton employees, is a former federal prosecutor. He was appointed in March to investigate allegations of fraud and mismanagement on behalf of the company.

In his request for documents, Hochberg said it's likely that Grant Thornton not only provided accounting services to Bennett but also to other top Refco executives. He sought records related to services that might have been provided to Robert Trosten, the company's former chief financial officer; Santo C. Maggio, its former executive vice president; and Philip Silverman, its former corporate secretary.

Hochberg also sought billing records identifying the Grant Thornton professionals who performed Refco's audits between August 2002 and November 2005. He specifically sought the personnel files of Ramler and three other current or former Grant Thornton employees.