An Indian-born naturalized United States citizen has had his citizenship revoked, making him the first casualty of a joint government operation that may lead to thousands more potentially facing deportation after having been granted citizenship, Rewire reports.

In an announcement on January 9, the Department of Justice said in a memo that Baljinder Singh, also known as Davinder Singh, is no longer a naturalized U.S. citizen after the government learned that he may not have gained citizenship lawfully. His citizenship was revoked by a U.S. District Court judge, and his status was reverted to lawful permanent resident. Singh is one of about 315,000 people whose fingerprint data is missing from the centralized digital fingerprint repository, meaning it's possible that some of those people may have entered the United States using different identities. Rewire points out that, because the government didn't use fingerprint data effectively, those who were naturalized before fingerprint records were digitized could be subject to the same process as Singh. The effort to identify suspicious cases is known as Operation Janus and is a joint operation between the Department of Homeland Security (DHS) and U.S. Citizenship and Immigration Services (USCIS). It was announced in September 2016.

The operation began after it was revealed that USCIS granted citizenship to "at least 858 individuals ordered deported or removed under another identity when, during the naturalization process, their digital fingerprint records were not available," according to a 2016 DHS memo cited by Rewire.

According to the DOJ, Singh entered the United States by plane in 1991 without travel documents or identification and gave the name Davinder Singh. After allegedly failing to appear for his immigration hearing, he was ordered deported in January 1992. But in February of that same year, the DOJ says Singh applied for asylum using the name Baljinder Singh. He was naturalized in 2006 under that name, after he married a woman from the U.S. Singh's new status as a lawful permanent resident puts him at risk for deportation.

Many on social media have reacted to the announcement. Some have called it a mechanism to deport documented immigrants.

Related: What It’s Like to Be a Teen Living in an Immigration Detention Center