Two workers were killed and seven others injured as the roof of an under-construction building collapsed at Barapukuria coalmine site in Dinajpur yesterday.  The deceased are: Proshanta Roy, 19, of Chowhati village of Parbatipur upazila, and Akash, 36, of Malipara village of Phulbari upazila. The injured were hospitalised.  According to officials, a one-storey building, about