(CNN) Seventy people have died in floods that ravaged parts of the coastal province of KwaZulu-Natal in South Africa's southeast, local authorities said.

Acting KwaZulu-Natal Premier Sihle Zikalala said in a press briefing Thursday morning that the death toll had risen from the previously reported 51.

"We are devasted by the increased numbers of fatalities," Zikalala said.

"It was the first time in KwaZulu-Natal where we lost people in this great number."

The flooding began on Monday after heavy rain caused mudslides in several towns in Durban, the largest city in KwaZulu-Natal, government spokesman Lennox Mabaso told CNN.