WASHINGTON — As a 26-year-old Muslim American man who spent 18 months in Yemen before heading home to Virginia in early May, Yahya Wehelie caught the attention of the FBI. Agents stopped him while he was changing planes in Cairo, told him he was on the no-fly list and questioned him about his contacts with another American in Yemen, one accused of joining al-Qaida and fatally shooting a hospital guard.

For six weeks, Wehelie has been in limbo in the Egyptian capital. He and his parents say he has no radical views, despises al-Qaida and merely wants to get home to complete his education and get a job.

But after many hours of questioning by FBI agents, he remains on the no-fly list. When he offered to fly home handcuffed and flanked by air marshals, Wehelie said, FBI agents turned him down.

"The lady told me that Columbus sailed the ocean blue a long time ago when there were no planes," Wehelie said in a telephone interview from Cairo. "I’m an innocent American in exile, and I have no way to get home."

Wehelie’s predicament reflects the aggressive response of U.S. counterterrorism officials to recent close calls with major terrorist plots: last year’s foiled plan to blow up the New York City subway; the failed attempt to take down an airliner headed for Detroit on Dec. 25; and the fizzled car bombing in Times Square on May 1. The case also illustrates the daunting challenge, both for people like Wehelie and for their FBI questioners, of proving that they pose no security threat.

Accused after the Dec. 25 near-miss of failing to keep the would-be bomber off the plane to Detroit, the government’s Terrorist Screening Center has since doubled the no-fly list to 8,000 names, according to a counterterrorism official who discussed the closely held numbers on the condition that he not be identified.

Counterterrorism officials have focused especially on Yemen, where the Dec. 25 bomber was trained. Traditionally, Yemen has been a popular and inexpensive place for Americans and others to study Arabic.

At least three Americans have been detained in recent weeks by the Yemeni authorities on suspicion of terrorist connections, and civil liberties advocates have identified a half-dozen Americans or legal U.S. residents on the no-fly list who are stranded abroad, most of them after visiting Yemen.

On Tuesday, the Council on American-Islamic Relations, a Washington-based group that has been working with Wehelie’s family, wrote to Attorney General Eric H. Holder Jr. to protest what its executive director, Nihad Awad, called "apparently illegal pressure tactics" against Muslim American travelers.

"If the F.B.I. wishes to question American citizens, they should be allowed to return to the United States, where they will be able to maintain their constitutional rights free of threats or intimidation," Awad wrote.

Awad noted that Yahya Wehelie’s younger brother, Yusuf, 19, who was stopped with him in Cairo, faced a shorter but even more harrowing time in Egypt. Questioned first by the FBI , Yusuf was later held for three days by Egyptian security officers, blindfolded, chained to a wall and roughed up before being allowed to travel home May 12, he said in an interview.

The American Civil Liberties Union says it has been contacted by a dozen people who say they have been improperly placed on the no-fly list since December, half of them Americans abroad.

"For many of these Americans, placement on the no-fly list effectively amounts to banishment from their country," said Ben Wizner, a senior staff attorney with the ACLU. He called such treatment "both unfair and unconstitutional."

An FBI spokesman, Michael P. Kortan, said that as a matter of policy, the bureau did not comment on who was on a watch list. But he said the recent plots showed the need "to remain vigilant and thoroughly investigate every lead."

"In conducting such investigations," Kortan said, "the FBI is always careful to protect the civil rights and privacy concerns of all Americans, including individuals in minority and ethnic communities."

Advocacy groups say they are trying to help Americans stranded in Yemen, Egypt, Colombia and Croatia, among other countries. At least one American, Raymond Earl Knaeble IV, who studied in Yemen and is now in Colombia, was returned to Colombia by Mexican authorities after he sought to cross the border into the United States, the groups say.

The no-fly list gives U.S. authorities greater leverage in assessing travelers who are under suspicion, because to reverse the flying ban many are willing to undergo hours of questioning.

But sometimes the questioning concludes neither with criminal charges nor with permission to fly. The Transportation Security Administration has a procedure allowing people to challenge their watch list status in cases of mistaken identity or name mix-up, but Wehelie does not fit those categories.

Wehelie was born and raised in the Virginia suburbs of Washington with his five siblings by Abdirizak Wehelie, 58, and Shamsa Noor, 54, Somali immigrants who met in the United States and married in 1981.

He graduated from Lake Braddock High School in Burke, Va., and briefly attended Norfolk State University. He worked in a medical lab and held other jobs, but he was arrested for marijuana possession and reckless driving, and his parents felt he was adrift, he said from Cairo.

In 2008, they insisted that he travel to Yemen, where they thought he could study Arabic, expand his horizons and perhaps find a wife.

"That’s the crazy thing — I was the one who made him go," said his mother.

Wehelie studied computer science at Lebanese International University in Sana, the Yemeni capital, he said, and last year he married a Somali woman in Yemen. And in the small American expatriate community, he said, he met Sharif Mobley, the New Jersey man who was later accused of joining al-Qaida and killing a Yemeni guard. Wehelie said their handful of encounters were brief and casual, the innocent small talk of two expatriates.

"It was just, ‘Hey, how you doing?"’ Wehelie said. The FBI’s suspicions are misplaced, he said: "I’m not even a religious person. I hate al-Qaida. I don’t like anything that jeopardizes my country and my family."

Evidently the FBI is not convinced. The U.S. authorities in Cairo canceled his passport and issued a new one Sunday with the notation, "valid only for return to the United States before Sept. 12, 2010," Wehelie said. That is his goal, he said, but he has no idea how to get home.

© 2010 The New York Times Company