Senate Judiciary Committee ranking member Chuck GrassleyCharles (Chuck) Ernest GrassleyFBI informant gathered years of evidence on Russian push for US nuclear fuel deals, including Uranium One, memos show Klobuchar taking over Franken's sexual assault bill Lawyer: Kushner is 'the hero' in campaign emails regarding Russia MORE (R-Iowa), along with a bipartisan group of 16 other senators, called on Attorney General Eric HolderEric H. HolderSessions defends Lynch's use of an email pseudonym: 'I have a pseudonym' Holder: Sessions is ‘racially insensitive’ and ‘racially unaware’ Let's start giving media manipulation the attention it deserves MORE this week to conduct a "comprehensive and exhaustive investigation" into the "potentially illegal misappropriation of funds" from MF Global customers.

"If the Department's ongoing investigation uncovers illegal actions, criminal prosecution should be pursued without hesitation," the senators wrote to Holder on Wednesday. "In order to get to the bottom of this, we urge federal agents to use every legal resource available."

The letter added that the bankruptcy of MF Global is posing the risk that thousands of farmers and other Americans stand to lose money in their accounts, even though federal rules require collateral to be held in customer segregated accounts.

"If credible evidence of illegalities is found by the investigation, significant resources should be utilized to prosecute those responsible," the letter said.

The bankruptcy has revealed that MF Global might have made proprietary investments with the collateral of its customers. The bankruptcy was prompted by fears that MF Global held too much risky sovereign debt.

Democrats on the letter are Senate Finance Committee Chairman Max BaucusMax Sieben BaucusBooker tries to find the right lane  Top Lobbyists 2017: Hired Guns GOP tries to keep spotlight on taxes amid Mueller charges MORE (Mont.) and Sens. Ben Nelson (Neb.), Kent Conrad (N.D.), Sherrod BrownSherrod Campbell BrownScott Garrett poses real threat to EXIM Bank, small businesses Class warfare fight erupts over tax bills Senators Hatch, Brown have heated exchange on GOP tax plan MORE (Ohio) and Amy KlobucharAmy Jean KlobucharKlobuchar taking over Franken's sexual assault bill Tech beefs up lobbying amid Russia scrutiny Facebook wants 'flexibility' in political advertising regs MORE (Minn.).