Congressional leaders are challenging a U.S. Attorney's denial that the Justice Department shut down a federal espionage investigation involving the illegal transfer of U.S. space defense weapons technology to foreign countries, including China, The Washington Examiner has learned.

Melinda Haag, the U.S. Attorney for Northern California, also denied that she had ever requested authority to prosecute anybody as a result of the espionage investigation.

But Sen. Charles Grassley, R-IA, and Representatives Lamar Smith, R-TX, and Frank Wolf, R-VA, say Haag's denials don't square with evidence they've reviewed and they wonder if Justice Department or White House officials interfered with a potentially explosive espionage investigation or if "politics played a role in the prosecutorial decisions made in this case."

"Your statement conflicts factually with information we received from federal law enforcement," Wolf, Smith and Grassley said in letters sent today to Haag and Assistant U.S. Attorney General Lisa O. Monaco questioning the abrupt end to an FBI national security investigation and grand jury probe.

At the center of the controversy is cancellation of a national security probe once led by Assistant U.S. Attorney Gary Fry. Frustrating attempts by foreign powers to steal U.S. space weapons technology have long been priorities for the FBI, the Department of Homeland Security and NASA's Inspector General.

The technology reportedly involves U.S. weapons capable of operating from space to defend the United States against international ballistic missile attacks.

Grassley, Smith and Wolf believe Fry was looking into charges of the unauthorized transfer of the military's space weapons technology to foreign nationals working at NASA's Ames Research Center near San Francisco.

In a Feb. 8 letter obtained by The Washington Examiner, Wolf and Smith first publicly charged something was amiss with the investigation in letters to FBI Director Robert Mueller and to the Justice Department's Inspector General.

Then on Feb. 12, Haag stated the "allegations are untrue" that her office sought Justice Department authority to bring charges against NASA officials.

"No such request was made, and no such denial was received," she said in a statement to The Washington Examiner.

The congressmen want to know details of Fry's removal and replacement by Assistant U.S. Attorney Elise Becker. They also asked Haag if she had communicated with the Justice Department, the Executive Office of the President or the White House about the national security investigation.

The congressional leaders also asked Monaco if the Attorney General's office communicated with Haag or with the White House over the probe.

Since his appointment as director of Ames in 2006, S. Pete Worden has surrounded himself with foreign nationals and invited foreigners who allegedly lacked national security clearances to spend extended time at Ames. In 2009, for example, he invited 170 foreign nationals from 40 countries to spend nine weeks at Ames.

In their Feb. 8 letter, Wolf and Smith charge the illegal technology transfer was potentially made "with the tacit or direct approval of the center's leadership."

Wolf and Smith have significant clout with the agency since the former is chairman of the House appropriations subcommittee that oversees funding for NASA.

Smith is chairman of the House Science, Space and Technology committee.

Grassley is the ranking Republican on the Senate Judiciary Committee.

Richard Pollock is a member of The Washington Examiner's Watchdog investigative reporting team. He can be reached at