The Johannesburg power company City Power was hit with a ransomware attack on July 25 which compromised its databases, applications and networks.

As a result, residents of the South African economic hub were unable to purchase electricity through City Power’s prepaid vending system, leaving them without power. The issue might also impact City Power’s ability to respond to outages, DW reports.

The Johannesburg municipality said on Twitter, “Customers should not panic as none of their details were compromised. We apologise for the inconvenience caused to the people of the City of Joburg. Please be patient with us, we expect to have everything back in order by the end of Thursday.”

Terence Jackson, CSO at Thycotic said there hasn’t yet been mention of a ransom request, but due to the severity of the attack, he’s sure it will be a healthy one.

 “It will also be interesting to see if the Power Body has properly backed up its data,” he said.

The crippling attack came just one day after City Power issued a press release stating it was prone to unplanned outages due to cold weather capacity constraints.