MUMBAI, Sept. 21 -- Metro construction sites across the city continue to pose a serious threat to motorists and commuters, with falling objects putting lives at risk. A 23-year-old man suffered serious injuries when a cement block fell on his head from an under-construction Metro bridge at Kashimira on Sunday evening, just a day after a 54-year-old plumber and delivery executive was killed by a falling iron barricade at a Metro 4 construction site in Vikhroli West. The latest incident took place in Mira Road when the injured man, identified as Shadab, stopped by the roadside to answer a phone call while crossing the area. He was allegedly struck by the cement block while near the under-construction Metro structure. Shadab sustained serious injuries and is currently undergoing surgery at Wockhardt Hospital in Mira Road. According to those familiar with the incident, he remained lying on the road for nearly an hour after being injured. Large vehicles parked along the roadside reportedly obstructed the view of motorists and passers-by, delaying his discovery. He was eventually spotted by a passer-by and taken to the hospital in an autorickshaw. Police have registered an FIR over negligence and are expected to record Shadab's statement to establish the exact sequence of events. MMRDA officials said the Kashimira location is an under-construction site and that entry into such areas is restricted, with safety gear mandatory for those entering the work zone. Officials said the injured man was not wearing safety gear and that an investigation into the incident has been initiated....