Public Protector Thuli Madonsela has agreed to consider the DA's request for a probe into the Gauteng e-tolling contracts, the party said on Wednesday.
"Public Protector Thuli Madonsela has responded to my request for an investigation into the Gauteng e-toll contracts, including a possible link with arms deal corruption," Democratic Alliance Gauteng caucus leader Jack Bloom said.
He received an e-mail from her on Wednesday morning to say the matter would be assessed to establish jurisdiction and merit, among other things.
"Like the arms deal, questions about possible corruption in the e-toll contracts will not go away until there is a credible investigation," he said.
"Speculation that something is being hidden has increased with the unexplained resignation of [SA National Roads Agency Limited] CEO Nazir Alli.
"The truth needs to come out."
The protector's spokeswoman Kgalalelo Msibi confirmed the communication with Bloom.
On Thursday, the DA said it had asked for an investigation on the grounds that suspicion was high that politically-connected people may have benefited from the plan to toll major highways around Johannesburg.
Bloom said there were reportedly allegations of links between Swedish companies involved in an arms deal and Austrian company Kapsch TrafficCom. He said there were also 35 sub-contracts with confidentiality clauses.
Alli resigned suddenly on Monday, just over a week after the Opposition to Urban Tolling Alliance (Outa) was granted an urgent interdict to stop the launch of tolling on 185km of highways around Johannesburg.
The project has since been put on hold and it is not yet clear what Sanral's next move will be.
Reasons were not given for Alli's resignation. He will remain in office until June 3.