Senate Judiciary Committee ranking member Chuck GrassleyCharles (Chuck) Ernest GrassleyPavlich: The claim Trump let the mentally ill get guns is a lie Congress fails miserably: For Asian-Americans, immigration proposals are personal attacks Grassley, Dems step up battle over judicial nominees MORE (R-Iowa), along with a bipartisan group of 16 other senators, called on Attorney General Eric HolderEric Himpton HolderPavlich: The claim Trump let the mentally ill get guns is a lie Pennsylvania Supreme Court releases new congressional map 36 people who could challenge Trump in 2020 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 Baucus2020 Dems pose a big dilemma for Schumer Steady American leadership is key to success with China and Korea Orrin Hatch, ‘a tough old bird,’ got a lot done in the Senate MORE (Mont.) and Sens. Ben Nelson (Neb.), Kent Conrad (N.D.), Sherrod BrownSherrod Campbell BrownLawmaker interest in NAFTA intensifies amid Trump moves Dem senator shares photo praising LeBron James after Laura Ingraham attacks Trump gets recommendation for steep curbs on imported steel, risking trade war MORE (Ohio) and Amy KlobucharAmy Jean KlobucharOvernight Health Care: Trump eases rules on insurance outside ObamaCare | HHS office on religious rights gets 300 complaints in a month | GOP chair eyes opioid bill vote by Memorial Day Overnight Regulation: Trump to take steps to ban bump stocks | Trump eases rules on insurance sold outside of ObamaCare | FCC to officially rescind net neutrality Thursday | Obama EPA chief: Reg rollback won't stand Dems seek reversal of nursing home regulatory rollback MORE (Minn.).