MINNEAPOLIS - The mother of an American freelance journalist said Monday she was concerned for the safety and welfare of her son and two others believed to have been arrested by Iranian authorities after going on a hiking trip in neighbouring Iraq.

In Washington, Secretary of State Hillary Rodham Clinton appealed to Iran for information on the three Americans to help determine their whereabouts.

"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," Clinton told reporters. "We asked our Swiss partners ... to please pursue our inquiries to determine the status of the three missing Americans."

A Kurdish official in northern Iraq 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.

Cindy Hickey told The Associated Press that her son, Shane Bauer, was one of the three missing Americans. Hickey, who lives in Pine City, Minnesota, said she hopes they return safely to the U.S.

"Our family is concerned about the safety and welfare" of the three, Hickey told the AP. She refused to comment further.

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.

One of the other missing Americans has been identified by family members as Joshua Fattal. His father, Jacob, told the AP on Monday that he didn't have any updates from the State Department about his son, who graduated from the same university as Bauer. Jacob Fattal declined to discuss how his son knew the other hikers.

"All we care about is the well-being of Josh and his two hiker friends," said Jacob Fattal, who lives in Elkins Park, Pennsylvania.

From January to June, Fattal travelled overseas as a teaching assistant with the International Honors Program, said the Boston-based program's President Joan Tiffany.

"He's a very thoughtful, caring person, soft-spoken, smart, bright. Has lots of travel experience and is someone that I would expect to be an experienced camper," Tiffany said.

The identity of the third American has not been confirmed, but other media reports have identified her as Sarah Shourd. Sandy Close, executive director of Pacific News Service where Bauer used to work, said one of Bauer's good friends told her Saturday that Shourd was taken into custody with Bauer, but she had no other details.

In a telephone interview, Hickey told the AP that her son was missing along with "Sarah and Josh," but she wouldn't elaborate further.

A fourth American, Shon Meckfessel, skipped the hike because he had a cold, his grandmother has said. The linguistics student called her Saturday from the American Embassy in Baghdad, she said.

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

Switzerland has represented U.S. interests in Iran since Washington broke off ties with Tehran after the 1979 Islamic Revolution and the takeover of the U.S. Embassy in Tehran by militant students. The two countries are locked in a bitter dispute over Iran's nuclear ambitions and U.S. allegations that Iran aides Shiite militants in Iraq.

"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."

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."