Construction workers were injured and “concrete bullets” fired into a car during an industrial explosion at a CBD worksite on Saturday afternoon.

Emergency services were called to Southbank's Australia 108 construction site, dubbed the highest residences in the southern hemisphere, after reports of a high pressure explosion shortly before 1pm.

Four men were injured in the industrial incident on Saturday. Credit:Scott McNaughton

Horrified witnesses said two workers were blown more than 15 metres onto the road, near the corner of City Road and Southbank Boulevard, by the force of the explosion with concrete and aggregate blasted across the the worksite.

One witness said pipes had been pumping concrete from a truck up more than 100 floors into the building when the cleaning mechanism "exploded".