A South African-born man, who now works as a police officer in the United States (US) state of Wisconsin, has been detained by federal immigration agents.

Local broadcaster WBAY reports that 21-year-old Carel Aaron Van Der Merwe was arrested at Madison’s airport on Thursday.

His lawyer says he holds valid work authorisation and has a pending asylum application. US authorities allege he overstayed his permitted admission.

According to broadcaster WBAY, immigration agents arrested Van Der Merwe while he waited to board a domestic flight.

His lawyer says he entered America legally as a child, remains included in his father’s pending asylum application and has permission to work until 2030.

But Homeland Security told the broadcaster he overstayed his admission, saying work authorisation or a pending application does not confer legal status. Authorities say he remains detained pending removal proceedings. His lawyer plans to seek release on bond.