Steve Smith says David Warner's altercation with Quinton de Kock came after the South African batsman "got personal" with the Australia vice-captain.
Warner and De Kock clashed during the fourth day of the first Test in Durban, the pair exchanging words as the players made their way up the stairs for tea.
South African television footage appeared to show Warner having to be pulled away from De Kock by Smith and Usman Khawaja.
The on-field umpires and match referee will look into the incident after both Cricket Australia and Cricket South Africa confirmed they had been warned about the players' behaviour on Sunday.
When asked about the exchange in his post-match media conference, Smith said he believes his team-mate was provoked at Kingsmead.
"Quinton got quite personal and provoked an emotional response from Davey," he said after Australia wrapped up a 118-run win on Monday.
"We were certainly very chirpy out on the field as well. As far as I am aware we didn't get personal toward Quinton.
"Those things are not on, you can't be getting into someone's personal life like that.
"That's crossing the line in my opinion.
"Obviously now it is in the hands of the officials. It's just about playing in the spirit of the game, we are men playing a competitive sport ... at times we need to pull things back."