The Maryland Transit Administration announced Thursday that it was indefinitely suspending light rail service on its north-south line starting Friday, citing recent mechanical issues that necessitate inspection of the entire fleet of 53 rail cars. The agency will begin shuttle bus service at all light rail stations starting Friday, pulling about 30 buses off their regular routes to fill the gap. MTA Administrator Holly Arnold acknowledged at an emergency news conference Thursday evening that this could have a ripple effect on service levels for other bus lines, and she said members of her team are doing everything they can to fix the light rail fleet quickly.