Criminality was the likely cause of the collapse of seven pylons, which supported 132kV powerlines, on the N4 in Pretoria on Sunday night, according to City of Tshwane Mayor Cilliers Brink.

"There are now clear indications that at least three of the pylons had been vandalised. So, indeed, there are strong indications that criminality played a role here," he said in an update on Monday. 

Initial reports indicated that six pylons had collapsed, but the City said on Monday evening that "seven powerline structures (pylons)" collapsed.

It caused a car pile-up which left at least two people injured. 

Eskom has been asked to help supply structures for the lines.

The N4 was reopened on Monday afternoon. 

The City is also investigating a photo that accompanied a tweet posted last year to warn of a possible collapse. It is probing whether the powerline in the tweet is indeed one situated in the area where the collapse occurred.