They helped to escort workers off the site and by 4pm all parties had dispersed.
Hundreds of union members gathered again on Wednesday morning, with police returning to the site to ensure public safety.
Premier Daniel Andrews said the protest could “potentially spread the virus”.
“I want to be very clear that no gathering that size is appropriate no matter what the cause, no matter what the issue, no matter what the reason, because all those sorts of gatherings do is potentially spread that virus so police and public health officials will deal with that matter,” he told radio station 3AW.
“But I just urge anyone, there’s ways to make your point, there are ways to be heard. Spreading the virus is in no one’s interest, no one”.
Police Minister Lisa Neville told the radio station she understood that police would fine those not abiding by the rules unless they cooperate with social distancing guidelines.
On Tuesday night, CFMMEU Victorian state secretary John Setka said the two union officials were “just doing their job when attacked by a bunch of cowards”.
“Members’ safety is our main priority. This is unacceptable,” he tweeted.
The left lane of Toorak Road is closed in both directions between Auburn Road and Tooronga Road, and the speed limit decreased to 40km/h.
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