The four police were killed on Wednesday evening as they were dealing with the Porsche driver on the Eastern Freeway in Kew.

A refrigerated truck veered to the left and hit them at 100km/h as they stood in the emergency lane.

Details of exactly how the crash happened remains unclear. The Victorian police commissioner, Graham Ashton, said on Thursday two officers had intercepted a Porsche 911 that was reportedly travelling at 140km/h just before 5pm on Wednesday afternoon.

The two officers drug-tested the driver, identified as Pusey. After he allegedly returned a positive result, the officers decided to impound the car, Ashton said. Shortly after two highway patrol officers were called to assist at the scene, a large refrigerated truck drove into the four officers.