The immigration process used to admit an Afghanistan national, who has been charged with planning a terrorist attack in the United States on Election Day, has come under scrutiny.

The FBI arrested Nasir Ahmad Tawhedi, 27, Monday in Oklahoma City after unearthing his alleged plot to carry out a large-scale Nov. 5 attack on public crowds. Tawhedi had pledged support to the Islamic State, which the U.S. has designated as a foreign terrorist organization.