Lawmakers looking into whether "political considerations" helped stonewall a federal probe into the transfer of sensitive weapons technology from a NASA center on Wednesday challenged a top U.S. attorney who claimed the allegations are "untrue."
Melinda Haag, the U.S. attorney for the Northern District of California, recently denied claims that her office was blocked by the Justice Department when it tried to proceed with the case.
But Republican Reps. Frank Wolf, R-Va., and Lamar Smith, R-Texas -- along with Sen. Charles Grassley, R-Iowa -- wrote in a letter to Haag Wednesday that the statement "conflicts factually with information we received from federal law enforcement."
The lawmakers reiterated allegations "that politics played a role" in the handling of the case. They cited claims that a witness was supposed to testify before a grand jury in February 2011, "but this witness's appearance was cancelled abruptly and not rescheduled."
Whistleblower documents obtained last week by FoxNews.com tell a similar story. The allegations surround the Ames Research Center in California. The claims originate with several past and current NASA employees concerned with the systemic leak of highly sensitive information relating to missile defense systems, as well as what they call a troubled investigation into the leak.
The documents claim the FBI has been working with other agencies since 2009 on an investigation into foreign nationals working at Ames.
The accusations stem from a reported violation of the International Traffic in Arms Regulation (ITAR), which governs the export of defense weaponry. The sources allege that Ames Center Director Simon P. "Pete" Worden and another British citizen shared sensitive technology with individuals from foreign countries including China, South Korea and Saudi Arabia.
Worden told FoxNews.com the accusations were "rubbish."
"I take very seriously our responsibility to safeguard sensitive information. I say this unambiguously - I have not, would not, and could not impede a law enforcement investigation. To the best of my knowledge I am not the subject of a current investigation," he said in a statement.
The Republican lawmakers, in letters to both Haag and Assistant Attorney General Lisa Monaco at the Justice Department in Washington, asked for information on any communications between the U.S. attorney's office in California and the Justice Department, White House and NASA.