Three Americans who were arrested after crossing into Iran have been accused of being spies, according to a local report.

Tehran-based television news channel al-Alam quoted an Iraqi police officer as saying the trio were “working with the CIA.”

The Swiss Embassy in Tehran was working to learn more about the Americans' fate through its contacts with the Iranian Foreign Ministry, spokeswoman Nadine Olivieri said. Switzerland represents U.S. interests in Iran.

The mother of one of the Americans said Monday she is concerned for the safety and welfare of her son and the two others.

Shane Bauer's mother, Cindy Hickey, said her son is one of the three Americans believed to have been arrested by Iranian authorities last week on a hiking trip in northern Iraq. Hickey, who lives in Pine City, Minn.,

"Our family is concerned about the safety and welfare" of the three, Hickey, who lives in Pine City, Minn., told The Associated Press. She refused to comment further.

A Kurdish official in Iraq has said the three contacted a colleague to say they had entered Iran by mistake on Friday and were surrounded by troops. Iran's state television later said the Americans were arrested after they did not heed warnings from Iranian border guards.

Clinton appeal

One of the other two Americans has been identified as Joshua Fattal. Fattal's mother, Laura Fattal of Elkins Park, Pa., issued a brief statement on Sunday expressing the family's concern.

NBC News said the third American was Sarah Shourd. A fourth American, Shon Meckfessel, skipped the hike because he had a cold, his grandmother has said.

Bauer is a freelance journalist and photographer based in the Middle East who has reported from Iraq, Syria, Sudan's Darfur region and Yemen, according to his Web site. He grew up in Minnesota and graduated from the University of California-Berkeley with a degree in Peace and Conflict Studies, the site said.

Earlier Monday, Secretary of State Hillary Rodham Clinton appealed to Iran for information on the missing Americans.

Clinton said that Swiss diplomats who represent U.S. interests in Iran were asking officials from the Iranian Foreign Ministry for details but had not yet gotten official confirmation of the trio's arrest. She asked that Iran determine the facts of the case and to "return them as quickly as possible."

"As of a few hours ago, we did not yet have official confirmation that the Iranian government or an instrument of the Iranian government were holding the three missing Americans," she told reporters in Washington. "We asked our Swiss partners ... to please pursue our inquiries to determine the status of the three missing Americans."

"Obviously, we are concerned," Clinton said. "We want this matter brought to a resolution as soon as possible and we call on the Iranian government to help us determine the whereabouts of the three missing Americans and return them as quickly as possible."

Swiss intermediary

State Department spokesman P.J. Crowley told reporters later that the Swiss ambassador in Tehran met with Iranian officials Sunday. The Iranians told the Swiss that they could not confirm the detention of the Americans, Crowley said.

Crowley said the fourth American who did not accompany the missing hikers has provided good information to U.S. officials in Baghdad. He did not elaborate.

"We have three Americans who are missing. We want to know what happened to them," Crowley said. "Clearly, we want them back as quickly as possible."

Iran's state TV said the Americans were arrested after they did not heed warnings from Iranian border guards.

Al-Alam quoted Col. Anwar Haj Omar of the Halabja police force in northern Iraq as saying the three Americans were “agents” employed by the CIA.

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