The commission said her tweets might have been in violation of the right to human dignity.
SAHRC acting provincial manager Tammy Carter said the commission would notify Zille of the fresh probe next week.
“As the SAHRC, we have elected to deal with the matter as an own initiative complaint in terms of our complaints-handling procedures,” Carter said.
“The complaint will not be investigated as hate speech, but as a potential violation of human dignity.”
Zille also landed herself at odds with her party when she fired off a series of tweets which were deemed to have been in praise of the colonial era.
“For those claiming the legacy of colonialism was only negative, think of our independent judiciary, transport infrastructure, piped water, etc,” Zille tweeted.
“Would we have had a transition into specialised health care and medication without colonial influence? Just be honest, please,” a second tweet read.
In her defence, Zille wrote: “Many prominent people have repeatedly made the same point that I did, so why the mass hysteria?”
She added there were many “falsehoods relating to my series of 12 tweets on lessons learnt from my recent visit to Singapore”.
“One of those lessons was that Singapore, having suffered centuries of colonial oppression, succeeded in repurposing aspects of colonialism’s legacy on which they built an inclusive modern economy.
“This, among other things, has enabled its people to escape poverty within a generation,” Zille said in a letter.
Notwithstanding the Premier’s defence and apology, the DA announced last week that it had officially charged Zille over the debacle. However, the party stopped short of elaborating what the exact charge or charges were.
Provincial SAHRC commissioner Andre Gaum said: “Nationally, we have received quite a number of complaints regarding this issue. The matter will be registered and investigated.”
Gaum said Zille would be afforded an opportunity to defend herself.
“After that, we will make a finding,” he said. “If it is found, for an example, that there was a violation of human dignity, this matter could go as far as the Equality Court.”
Neither the SAHRC nor the DA would commit to time frames.
“The DA’s procedures involve hearings at which evidence is led and witnesses are cross-examined. The panel meets when the panel members, the accused member and his or her legal representative(s) are simultaneously available,” said James Selfe, the DA’s federal executive chairperson.
“Our office has not received correspondence from the SAHRC,” Zille’s spokesperson, Michael Mpofu, said on Thursday.