Two workers at a Manchester Township plant temporarily became ill Wednesday morning after inhaling a silica-type powder, leading to a four-hour hazardous-materials incident. The township's Alert Fire Co. and the county's haz-mat team were called to Engel Machinery Inc., at 3740 Board Road, about 7:35 a.m., Alert Fire Chief Joe Madzelan said. Workers had found a powdery substance on top of an unopened shipping box, and two of the workers became ill, he said.