Farlam commission of inquiry chairperson Ian Farlam has cautioned against intimidation after allegations of an altercation between two rival unions.
"Up to now there has been a harmonious atmosphere between members of the two unions," Farlam said on Thursday.
Karel Tip, for the National Union of Mineworkers (Num), told the commission that after proceedings on Wednesday, members of the Association of Mineworkers and Construction Union (Amcu) allegedly intimidated Num members in the parking lot.
He said about 40 people wearing Amcu T-shirts "more or less confronted the NUM members, in a fairly confrontational manner".
A song, translated as "kill the NUM" was sung, and police intervened, but no serious consequences ensued.
It appeared that most of the Amcu members were from Impala platinum mine, rather than Lonmin, he said.
Farlam said it was important that the commission be allowed to conduct its work in a harmonious atmosphere.
"I trust that all concerned will behave as well as they have done in the past, before this incident which allegedly happened," Farlam said.
On Thursday only a few people attending the commission's public hearings were wearing the red and green T-shirts associated with Num and Amcu respectively.
On Wednesday, however, there were many more and they sat on opposite sides of the auditorium.
The three-member commission is holding public hearings at the Rustenburg Civic Centre.
The other commissioners are senior advocates Bantubonke Tokota and Pingla Hemraj.
Thirty-four striking miners were shot dead on August 16 and 78 wounded when the police opened fire on them while trying to disperse a group gathered on a hill near the mine.
In the preceding week, 10 people, including two police officers and two security guards, were hacked to death near the mine.
President Jacob Zuma announced the commission in August.
Zuma said it would complete its work within four months, and would have to submit its final report a month later. – Sapa.