Police at the Stadium of Light are checking coaches carrying Pompey fans to make sure no flares or smoke bombs are on board.
The move this lunchtime comes after a flare was thrown during the corresponding league game in April.
Then, the game – which ended 1-1 – was interrupted for several minutes after the flare went off, leaving one supporter needing medical attention for smoke inhalation.
In May 18-year-old Pompey fan Samuel Parrott of Norton Drive, Fareham, was banned from games for three years at South Tyneside Magistrates’ Court after admitting ‘throwing an item at a designated football ground’.
After that Sunderland reduced the away fan allocation for Pompey games, including the semi-final of the play-offs between the two teams at the end of last season.