Four Metro cops may be in hot water for passing rocks placed on the N1 highway, where a Johannesburg man was ambushed and killed, police said on Wednesday.

"An internal investigation has revealed that two metro police patrol vehicles passed the rocks that were placed on the N1 highway, between the Malibongwe and William Nicol offramps," said Superintendent Wayne Minnaar.

Director David Tembe, Johannesburg metro police Head of Operations, has dismounted the four metro police officers concerned.

"They have been instructed to do foot patrolling pending the outcome of the investigation due to the seriousness of the matter," said Minnaar.

He said the patrol vehicles passed between 1.13am and 1.42am on 2 October, when Arren Mahabir (32), was shot and killed.

Mahabir's car hit the rocks placed by robbers hiding in the nearby bushes around 2.40am.

He was shot and killed as he and his fiancee, Valesh Naidoo, got out to change the burst tyre on their vehicle, after hitting the rocks.

Mahabir was on his way to Durban at the time of the incident.

Sapa