Both the persons did not have any legal documents, provincial census commissioner of Sindh Abdul Aleem Memon said while addressing reporters after winding up the first phase of census in eight districts of Sindh province.
The authorities, during census exercise, detained the two Indian nationals, claiming that they were living in Karachi "illegally", the Express Tribune reported.
"One has been arrested from Gulberg Town, Karachi and we have recovered a diary from his possession," he said.
They have been handed over to law enforcement agencies for further investigation, the official said.