Two Republican U.S. senators are calling on the Justice Department to explain the “questionable actions” of federal prosecutors who handled the criminal case against Maple Grove med-tech company Vascular Solutions and its CEO, Howard C. Root.

Federal jurors in west Texas found Root and Vascular Solutions not guilty on all counts in February after a grand jury indictment alleged a criminal conspiracy to market a medical device for varicose veins in ways that the Food and Drug Administration disapproved. The defense won the case solely by cross-examining prosecution witnesses, rather than calling any of its own.

Root has said prosecutors acted unethically to get the grand jury to indict him, by threatening witnesses to change their testimony and divulging grand jury testimony to other witnesses. On Monday, a spokeswoman said the Justice Department is working on a response to the allegations.

That response will go to Sens. Charles Grassley, R-Iowa, and Mike Lee, R-Utah, both members of the Senate Judiciary Committee, who sent a four-page letter to Deputy Attorney General Sally Quillian Yates last month asking about prosecutors’ conduct in the case. The letter gave Yates until June 2 to respond to more than a dozen written questions.

“We write regarding the questionable actions of federal prosecutors in connection with the prosecution,” the senators’ letter says. “As we have previously noted, prosecutors must be held to the same standards as the general public and are accountable for their conduct as representatives of the United States.”

Asked about the substance of the allegations, a Justice Department spokeswoman said by e-mail, “We respectfully disagree with Howard Root’s comments about the trial team.”

In an interview, Root repeated comments he has made in speaking engagements since his acquittal, saying prosecutors handling the case against him demonstrated “repulsive conduct.” He said his company spent $25 million with 14 law firms to defend itself and represent its employees, including Root, over five years, when no illegal acts occurred.

Root said Yates is on record with a widely debated legal doctrine, laid out in a document called the “Yates Memo,” which makes the targeting of high-ranking executives a priority in cases involving allegations of corporate wrongdoing.

“The Yates Memo says, we are not settling any investigation until we get individuals held responsible. That assumes that individuals have done something wrong,” Root said. “In a lot of cases, as in my case, no one had done anything wrong except the prosecutors.”

The senators’ letter lays out several specific allegations against the prosecutors in Root’s case, including the use of grand jury subpoenas to induce questioning outside the presence of a jury, divulging secret grand jury testimony to other witnesses, and telling witnesses to change their testimony or face a threat of firing and exclusion from working at any company that does business with Medicare.

Then-U.S. District Judge Fred Biery considered some of the same allegations in a motion to dismiss the case last November, and sided with the prosecutors. “The Court finds that attorneys for the government did not commit prosecutorial misconduct,” Biery wrote.

He ruled there was no evidence that the witnesses changed the testimony in response to the threats or that the reading of grand jury testimony to other witnesses prejudiced the grand jurors.

Root told investors in an April 25 earnings call that although the case was driven by what he called “abusive conduct,” the company’s legal team has concluded there is no legal means for the company to recover its costs defending against false charges.