Due to inspections that found "structural issues," NECN reports [2].
Boston Metro reports [3] the state wants federal transportation officials to shut the entire company down until it fixes the problems.
Links:
[1] http://www.universalhub.com/users/adamg
[2] http://www.necn.com/02/25/13/21-Fung-Wah-buses-taken-off-road-due-to-/landing.html?blockID=832797&feedID=11106
[3] http://www.metro.us/boston/news/local/2013/02/25/state-seeks-imminent-hazard-over-fung-wah-buses/
[4] http://www.universalhub.com/taxonomy/term/24
[5] http://www.universalhub.com/mbta/buses
[6] http://www.universalhub.com/taxonomy/term/410