For nearly a year, immigration authorities have detained and sought to deport a mentally ill man whose mother, lawyers and public records say was born in the United States and not Jamaica as he claims, a review by The Associated Press found.

Immigration and Customs Enforcement has no authority to detain U.S. citizens, but has long done so, usually for hours or days, when officers mistake identities or can’t immediately verify citizenship. Immigration lawyers say a nearly 10-month improper detention would be rare but not unprecedented.

The Department of Homeland Security, which oversees ICE, disputes that the man is a U.S. citizen and alleges, without providing evidence, that the birth certificate he submitted to obtain a U.S. passport that he held for 15 years was fraudulent. But AP’s review found documents that support claims by his mother and legal team that he was born in Florida and therefore not subject to ICE’s authority.