Washington (CNN) -- The U.S. government said Wednesday it is holding a Somali man on immigration violations, but gave no indication why the man was deemed to be a threat to a commercial jet that was denied permission to overfly the United States on Sunday.
However, the brother of Abdirahman Ali Gaal, the detained man, said U.S. officials may be suspicious because of Gaal's outspoken views about U.S. policy in the Middle East, his frequent comments on an Internet website, and his recent travel to Mauritania in northern Africa to study Islam.
Abdifatah Gaal described his brother as "confused" by the detention because he had been assured by U.S. authorities while overseas that there was no impediment to his return to the United States.
The case of Abdirahman Ali Gaal came to a head Sunday when U.S. authorities denied permission for the Aeromexico flight he was on -- traveling from Paris, France, to Mexico City, Mexico -- to overfly the United States.
The flight was diverted to Montreal, where Canadian officials took custody of Gaal before turning him over to U.S. officials Tuesday.
U.S. officials have since said that Gaal was on the "no fly" list, compiled by the government, of people banned from flying in the United States.
Matthew Chandler, a Department of Homeland Security spokesman, said Wednesday that Gaal was questioned by U.S. officials.
"In the course of that interview process, he was determined to be inadmissible to the United States and is currently being detained pending immigration proceedings," Chandler said.
Gaal admitted to having committed fraud when he applied for refugee status in Canada in October 2008 and to abandoning his "legal permanent residency" status in the United States by departing the U.S. for more than 10 months and applying for refugee status in Canada, a U.S. official told CNN on condition of not being identified by name.
Immigration issues of that sort, however, do not typically put a person on the "no fly" list, which includes about 6,000 people, the official acknowledged.
U.S. officials declined to provide any further information about the matter.
Gaal's brother, contacted Wednesday by CNN, said Gaal had strong political beliefs but has insisted he had done nothing wrong.
Abdifatah Gaal said his brother was critical of U.S. policies in the Middle East and aired his views on Paltalk, which hosts Internet chat forums. Several months ago, he said, his brother went to Mauritania in northern Africa to study Islam. While in Mauritania, Gaal received a call from his wife in Toronto, saying she had been visited by Canadian police looking for him.
Gaal then went to the U.S. Embassy in Mauritania and was told there was no impediment to him returning home, according to his brother. Gaal also called the FBI to check on his status, his brother said.
Gaal flew to Paris and on to Mexico City, and intended to travel to Seattle, Washington, where their mother lives, his brother said.
Abdifatah Gaal said his brother's arm was broken when he was removed from the aircraft in Montreal, even though, he said, Gaal did not resist. He said the family is trying to hire an immigration attorney to represent his brother.