Washington ? Ahmad Chalabi, the Iraqi politician suspected by U.S. authorities of having told Iran this spring that its secret communications code had been broken, was involved in another intercept episode nine years ago, according to senior administration officials.

Officials Thursday recounted an incident in early 1995 when Chalabi’s name turned up in an encrypted Iranian cable reporting a purported CIA-backed plan to assassinate Saddam Hussein, then Iraq’s president. The message was intercepted by U.S. intelligence and caused a major political stir in Washington.

Similarly, it was an intercept several weeks ago of another Iranian message — this one from an agent in Baghdad to his superiors in Tehran saying Chalabi had told him that U.S. intelligence was able to read Iran’s secret cables — that has triggered a major counterintelligence probe and concern about Washington’s future ability to monitor Iranian developments.

A U.S. law enforcement source who demanded anonymity because the investigation is secret said Thursday that FBI investigators had interviewed at least one Defense Department employee in Baghdad and had administered a polygraph test. More tests were planned, some involving officials at the Pentagon, the source said. But several senior defense officials said Thursday that they knew of no one at the Pentagon who had yet been approached by investigators.

FBI spokeswoman Debbie Weierman said the investigation was still at its early stage. Noting that Chalabi is a British citizen, she said that law enforcement officials also are trying to determine “to what extent he is covered by U.S. law barring disclosure of U.S. classified information.”

Chalabi, whose exile group — the Iraqi National Congress — has received more than $40 million in U.S. payments over the years, has denied that he disclosed secrets to Iran and has demanded that the Bush administration investigate the source of the leak about the investigation of him.

The 1995 incident arose at a time Chalabi was in northern Iraq, working with CIA backing against Saddam.