Muslim and civil rights groups are reporting an increasing number of Muslim citizens and permanent residents of the United States who have traveled abroad but are being told they are on the U.S. No-Fly List and are prohibited from returning to the United States.

No Iranians are known to have been caught in this net yet. The issue has become so serious that the American Civil Liberties Union (ACLU) filed a lawsuit June 30 on behalf of 10 U.S. citizens and lawful residents who have been prohibited by law enforcement from flying to or from the United States or over U.S. airspace. Moreover, each of the individuals named in the lawsuit said they never received an explanation as to why their names appeared on the list.

Ben Wizner, staff attorney with the ACLU National Security Project, said, "More and more Americans who have done nothing wrong find themselves unable to fly and, in some cases, unable to return to the U.S., without any explanation whatsoever from the government. A secret list that deprives people of the right to fly and places them into effective exile without any opportunity to object is both un-American and unconstitutional."

The civil liberties union and its affiliates in Oregon, Southern California, Northern California and New Mexico, filed the lawsuit against the U.S. Department of Justice, the FBI and the Terrorist Screening Center in the U.S. District Court for the District of Oregon.

The 10 plaintiffs named in the case are: Ayman Latif, Raymond Earl Knaeble, Steven Washburn, Samir Mohamed Ahmed Mohamed, Abdullatif Muthanna, Nagib Ali Ghaleb, Saleh A. Omar, Mohamed Sheikh Abdirahman Kariye, Adama Bah and Halime Sat.

Ayman Latif is a U.S. citizen and disabled Marine veteran living in Egypt who has been barred from flying to the United States. After FBI agents questioned him, they reportedly told him that the agents would be going on vacation for several weeks and would not be able to give him clearance to return to the United States until after their return.

Knaeble is a 29-year-old U.S. citizen and U.S. Army veteran who was trying to board a flight from Santa Marta, Colombia to the United States when officials stopped him. The California-born military contractor has been stuck in Colombia since March 14, after apparently being placed on the No-Fly List without explanation. He is currently being investigated by the Dallas FBI office.

Washburn, a U.S. citizen and U.S. Air Force veteran, was prevented from flying from Europe to the United States or Mexico. Eventually, he flew from Brazil to Peru and from Peru to Mexico, where he was detained and finally escorted across the border by authorities from the United States and Mexico.

Mohamed, Muthanna, Ghaleb and Saleh A. Omar, three American citizens and a green card holder, were barred from flying back to the United States after visiting their families in Yemen.

Kariye, a U.S. citizen and resident of Portland, Oregon, was not allowed to fly to visit his daughter who is in high school in Dubai.

Bah, a citizen of Guinea who has lived in the United States since she was granted political asylum at the age of two, was barred from flying from New York to Chicago for work.

Sat is a German citizen and lawful permanent resident of the United States. She lives in California with her U.S.-citizen husband who was prevented from flying from Long Beach, in southern California, to Oakland, in northern California, to attend a conference. Since then, he has had to cancel trips to participate in educational programs and was not allowed to attend a family reunion in Germany.

Airport and border security has been stepped up following the failed attempt by a passenger to take down a plane headed for Detroit on December 25, and much of the attention has focused on Yemen, where would-be "underwear" bomber Umar Farouk Abdulmutallab was trained.

Responding to the increased security and scrutiny against Muslims and Arab Americans, the Council on American Islamic Relations (CAIR) issued a travel advisory July 9 to American Muslims warning of what it called the risk of "forced exile" when trying to return to the United States after traveling abroad.

CAIR reported that it has heard of numerous cases of American Muslims stranded overseas after unknowingly being place on the government's No-Fly List. Some of those prevented from returning to their homes in the United States say they have been subjected to pressures from the FBI to give up the constitutionally guaranteed right to remain silent. Others have reported that their passports have been confiscated without due process. Still others report they have been pressured to become informants for the FBI.

The 10 plaintiffs named in the ACLU lawsuit are not the only people who have been prevented from returning to the United States.

Twenty-six-year-old Yahya Wehelie, an American citizen, was detained in early May after U.S. investigators grew suspicious of the time he spent in Yemen. Wehelie drew attention when he was returning home to Virginia after spending a year-and-a-half in Yemen. But Wehelie denies any links to terrorism, claims he hates Al-Qaeda and says he just wanted to come home to the United States.

Police detained Wehelie as he was changing planes in Cairo, where they notified him that his name was on the No-Fly List. There, he was reportedly questioned for hours about his contacts with another American man in Yemen, who was accused of joining Al-Qaeda and later killing a hospital guard. Wehelie was informed that the FBI will fly in from the United States to interrogate him. The man's family was reportedly asked to pay for his hotel in Cairo while he waits for the FBI agents.

Wehelie's 19-year-old brother, Yusuf, was also stopped with him in Cairo. According to Yusuf, he was questioned, detained for three days by Egyptian security officials, blindfolded, chained to a wall and physically roughed up before being released on May 12, when he was allowed to travel home.

Darryl Dalil Javid, 44, a native of Washington, D.C. who recently converted to Islam, was another American stopped as he tried to board a flight out of Yemen in January. Javid, who had moved to Yemen in 2005, took regular trips back to the United States to work as a facilities manager. He said his Yemeni visa had expired last year but that he was able to fly in and out of the United States without problems.

After the December 25 bombing attempt, Yemen began to deport people without valid visas. Javid said that when they tried to deport him, he could not find an airline that would let him fly to the United States. He said he spent a week at the airport in Istanbul, flying briefly to Morocco only to be turned back. He was finally sent back to Yemen, where he said he was held in a room full of detainees in the Interior Ministry.

Javid finally returned to the United States March 25. U.S. Embassy officials told him that he could buy a ticket on a specific flight carrying U.S. air marshals back to his mother's home in Maryland. He said the two-month ordeal cost him about $6,000.