Major League Baseball has told its 30 teams they must implement security screening for fans by 2015, either with hand-held metal detection or walk-through magnetometers.

"This procedure, which results from MLB's continuing work with the Department of Homeland Security to standardize security practices across the game, will be in addition to bag checks that are now uniform throughout MLB," baseball spokesman Michael Teevan said.

The Seattle Mariners announced that fans entering Safeco Field will have to walk through metal detectors starting with this year's opener, said AP.

"We conducted testing of these measures at the All-Star game and at both World Series venues last year, and we were pleased that it was effective and received without issue from fans," Teevan said.