The areas included Alexandra, Ivory Park, Diepsloot, Johannesburg and some areas in the Westonaria, Midvaal and the City of Tshwane.
In Soweto, only about 25% of the votes had been counted by 10am.
Democratic Alliance spokesman Solly Malatsi said his party celebrated when ANC dropped to below 50% in Gauteng and hoped it remained there until counting was completed.
"If it remains at 49.5%, it will need another party to govern. This is great news for the opposition," Malatsi said.
At around 11:15am with about 61% of voting districts declared, the ANC was at 49.6% in Gauteng.
More voting districts are expected to be declared later in the day.