However , after the Madrid train bombings in 2004 and the foiled plot to bomb the Yishun MRT Station , the operators deployed private , unarmed guards to patrol station platforms and check the belongings of commuters .
However , in the wake of heightened security concerns after the Madrid train bombings in 2004 and the foiled plot to bomb the Yishun MRT Station , the operators deployed private , unarmed guards to patrol station platforms and check the belongings of commuters .