Ten labourers were killed and three others critically injured when the slab of an under-construction building on which they were working suddenly crashed here on Friday, police said.The 13 labourers were working on the 14th floor of the under-construction tower of Pride Purple Constructions when the slab collapsed in the city's Balewadi area.All the workers fell in a heap below and eight of them were believed to have died instantly."We have taken his incident very seriously. We shall order an inspection of all such construction sites now to ascertain whether they are employing adequate safety measures of the workers," Pune Mayor Prashant Jagtap said.It is not known whether the labourers were wearing safety harnesses while working at that height or why a safety net was not erected below to stop any casualties.Meanwhile, the police have called the building contractor and the building owners for investigations into the slab crash.