The Federal Investigation Agency's (FIA's) Immigration & Anti-Human Trafficking Cell (I&AHTC) arrested four foreigners with fake visa extension here on Tuesday. The I&AHTC of FIA during verification of visas of four foreigners leaving for abroad at Quaid-e-Azam International Airport, Karachi, found their visa extension to be fake. The authorities detained all the four foreigners who stayed in Pakistan on fake visa extension.