The U.S. State Department says it is looking into reports that a fourth Iranian-American visiting Iran may be under detention. The White House said spy charges filed against three U.S. citizens by Tehran authorities are "preposterous." VOA's David Gollust reports from the State Department.

Officials here say they are trying to determine whether another Iranian-American visitor to Iran is being held by authorities and could face espionage charges.

The Iranian daily newspaper Kayhan, which is linked to political hard-liners, reported that Iranian-American businessman Ali Shakeri has been arrested and is accused of having links to opposition groups seeking to overthrow Iran's Islamic leadership.

Iranian authorities have not acknowledged the arrest of Shakeri, who is said to work for the Center for Citizen Peacebuilding at the University of California at Irvine. The New York-based Human Rights Watch said last week that associates of Shakeri had told the group he was under detention.

Haleh Esfandiari

On Tuesday, Iran said two U.S.-Iranian scholars, Haleh Esfandiari and Kian Tajbakhsh, were being held on spy charges, and that a third dual-national, Radio Farda journalist Parnaz Azima, faced similar charges but had not been arrested.

In a talk with reporters, State Department Deputy Spokesman Tom Casey said he could not confirm Shakeri's detention, but U.S. officials are concerned about a "pattern of harassment" of Iranian-Americans by Tehran authorities.

"It is absolutely inconceivable how this regime would think that individuals who are private citizens, who are visiting family members, who are conducting private activities, and who have been doing so for quite some time, somehow now pose a threat to the regime or are involved in activities of a political nature there," he said. "It is simply untrue, and what the regime need to do is just release these people and let them go back to their families."

At the White House, spokesman Tony Snow said the notion the detained Americans have been engaged in spying is "preposterous."

Some news reports have suggested Iran may be detaining American visitors as possible bargaining chips for the release of at least five Iranians held in northern Iraq for alleged involvement in attacks on U.S.-led coalition forces.

Tom Casey

But spokesman Casey said the Iranian government has not made that connection, and that the issue did not come up Monday when U.S. Ambassador to Iraq Ryan Crocker held a rare meeting with Iranian diplomats in Baghdad.

Casey said in any event there can be no comparison between cases like that of Haleh Esfandiari, a 67-year-old grandmother, and the terror suspects in Iraq.

"One needs to consider rather extreme difference here," he said. "Iran is arresting grandma. The multi-national forces are arresting people who are providing explosives and weapons, and training to use them, to individuals that are killing Americans, and killing Iraqis, both security forces and civilians. I think there is a great distinction there."

In comments to reporters traveling with her to Europe, Secretary of State Condoleezza Rice said the two issues are "wholly unconnected" and that Iran's treatment of the U.S. citizens is a "perversion of the rule of law."

Human Rights Watch has called the Iranian actions a "witch hunt."

The Washington-based Woodrow Wilson Center for International Scholars, which employs Esfandiari, said it was extremely disheartened by the news she faces charges.

Former Congressman Lee Hamilton, who heads the center, says Esfandiari has been interrogated about a $75 million U.S. program announced last year to fund pro-democracy programs in Iran, but that his organization receives no funding from it.