A pillar fall occurred on the active 002 Pillar Section that entrapped a Mobile Roof Support. Two MRS units were located in the No. 2 Entry and were blocked when rock fell from the left pillar lift and some of the material slid out in front of the MRS units. One of the MRS Units (# 3 MRS) was retrieved and the other (#4 MRS) was entrapped when the roof in the pillar line fell in.